FreeBSD/Linux Kernel Cross Reference
sys/conf/NOTES

     # $FreeBSD$
     #
     # NOTES -- Lines that can be cut/pasted into kernel and hints configs.
     #
     # Lines that begin with 'device', 'options', 'machine', 'ident', 'maxusers',
     # 'makeoptions', 'hints', etc. go into the kernel configuration that you
     # run config(8) with.
     #
     # Lines that begin with 'envvar hint.' should go into your hints file.
    # See /boot/device.hints and/or the 'hints' config(8) directive.
    #
    # Please use ``make LINT'' to create an old-style LINT file if you want to
    # do kernel test-builds.
    #
    # This file contains machine independent kernel configuration notes.  For
    # machine dependent notes, look in /sys/<arch>/conf/NOTES.
    #
    
    #
    # NOTES conventions and style guide:
    #
    # Large block comments should begin and end with a line containing only a
    # comment character.
    #
    # To describe a particular object, a block comment (if it exists) should
    # come first.  Next should come device, options, and hints lines in that
    # order.  All device and option lines must be described by a comment that
    # doesn't just expand the device or option name.  Use only a concise
    # comment on the same line if possible.  Very detailed descriptions of
    # devices and subsystems belong in man pages.
    #
    # A space followed by a tab separates 'options' from an option name.  Two
    # spaces followed by a tab separate 'device' from a device name.  Comments
    # after an option or device should use one space after the comment character.
    # To comment out a negative option that disables code and thus should not be
    # enabled for LINT builds, precede 'options' with "#!".
    #
    
    #
    # This is the ``identification'' of the kernel.  Usually this should
    # be the same as the name of your kernel.
    #
    ident           LINT
    
    #
    # The `maxusers' parameter controls the static sizing of a number of
    # internal system tables by a formula defined in subr_param.c.
    # Omitting this parameter or setting it to 0 will cause the system to
    # auto-size based on physical memory.
    #
    maxusers        10
    
    # To statically compile in device wiring instead of /boot/device.hints
    #hints          "LINT.hints"            # Default places to look for devices.
    
    # Use the following to compile in values accessible to the kernel
    # through getenv() (or kenv(1) in userland). The format of the file
    # is 'variable=value', see kenv(1)
    #
    #env            "LINT.env"
    
    #
    # The `makeoptions' parameter allows variables to be passed to the
    # generated Makefile in the build area.
    #
    # CONF_CFLAGS gives some extra compiler flags that are added to ${CFLAGS}
    # after most other flags.  Here we use it to inhibit use of non-optimal
    # gcc built-in functions (e.g., memcmp).
    #
    # DEBUG happens to be magic.
    # The following is equivalent to 'config -g KERNELNAME' and creates
    # 'kernel.debug' compiled with -g debugging as well as a normal
    # 'kernel'.  Use 'make install.debug' to install the debug kernel
    # but that isn't normally necessary as the debug symbols are not loaded
    # by the kernel and are not useful there anyway.
    #
    # KERNEL can be overridden so that you can change the default name of your
    # kernel.
    #
    # MODULES_OVERRIDE can be used to limit modules built to a specific list.
    #
    makeoptions     CONF_CFLAGS=-fno-builtin  #Don't allow use of memcmp, etc.
    #makeoptions    DEBUG=-g                #Build kernel with gdb(1) debug symbols
    #makeoptions    KERNEL=foo              #Build kernel "foo" and install "/foo"
    # Only build ext2fs module plus those parts of the sound system I need.
    #makeoptions    MODULES_OVERRIDE="ext2fs sound/sound sound/driver/maestro3"
    makeoptions     DESTDIR=/tmp
    
    #
    # FreeBSD processes are subject to certain limits to their consumption
    # of system resources.  See getrlimit(2) for more details.  Each
    # resource limit has two values, a "soft" limit and a "hard" limit.
    # The soft limits can be modified during normal system operation, but
    # the hard limits are set at boot time.  Their default values are
    # in sys/<arch>/include/vmparam.h.  There are two ways to change them:
    # 
    # 1.  Set the values at kernel build time.  The options below are one
    #     way to allow that limit to grow to 1GB.  They can be increased
    #     further by changing the parameters:
   #       
   # 2.  In /boot/loader.conf, set the tunables kern.maxswzone,
   #     kern.maxbcache, kern.maxtsiz, kern.dfldsiz, kern.maxdsiz,
   #     kern.dflssiz, kern.maxssiz and kern.sgrowsiz.
   #
   # The options in /boot/loader.conf override anything in the kernel
   # configuration file.  See the function init_param1 in
   # sys/kern/subr_param.c for more details.
   #
   
   options         MAXDSIZ=(1024UL*1024*1024)
   options         MAXSSIZ=(128UL*1024*1024)
   options         DFLDSIZ=(1024UL*1024*1024)
   
   #
   # BLKDEV_IOSIZE sets the default block size used in user block
   # device I/O.  Note that this value will be overridden by the label
   # when specifying a block device from a label with a non-0
   # partition blocksize.  The default is PAGE_SIZE.
   #
   options         BLKDEV_IOSIZE=8192
   
   #
   # MAXPHYS and DFLTPHYS
   #
   # These are the maximal and safe 'raw' I/O block device access sizes.
   # Reads and writes will be split into MAXPHYS chunks for known good
   # devices and DFLTPHYS for the rest. Some applications have better
   # performance with larger raw I/O access sizes. Note that certain VM
   # parameters are derived from these values and making them too large
   # can make an unbootable kernel.
   #
   # The defaults are 64K and 128K respectively.
   options         DFLTPHYS=(64*1024)
   options         MAXPHYS=(128*1024)
   
   
   # This allows you to actually store this configuration file into
   # the kernel binary itself. See config(8) for more details.
   #
   options         INCLUDE_CONFIG_FILE     # Include this file in kernel
   
   #
   # Compile-time defaults for various boot parameters
   #
   options         BOOTVERBOSE=1
   options         BOOTHOWTO=RB_MULTIPLE
   
   #
   # Compile-time defaults for dmesg boot tagging
   #
   # Default boot tag; may use 'kern.boot_tag' loader tunable to override.  The
   # current boot's tag is also exposed via the 'kern.boot_tag' sysctl.
   options         BOOT_TAG=\"\"
   # Maximum boot tag size the kernel's static buffer should accommodate.  Maximum
   # size for both BOOT_TAG and the assocated tunable.
   options         BOOT_TAG_SZ=32
   
   options         GEOM_BDE                # Disk encryption.
   options         GEOM_CACHE              # Disk cache.
   options         GEOM_CONCAT             # Disk concatenation.
   options         GEOM_ELI                # Disk encryption.
   options         GEOM_GATE               # Userland services.
   options         GEOM_JOURNAL            # Journaling.
   options         GEOM_LABEL              # Providers labelization.
   options         GEOM_LINUX_LVM          # Linux LVM2 volumes
   options         GEOM_MAP                # Map based partitioning
   options         GEOM_MIRROR             # Disk mirroring.
   options         GEOM_MULTIPATH          # Disk multipath
   options         GEOM_NOP                # Test class.
   options         GEOM_PART_APM           # Apple partitioning
   options         GEOM_PART_BSD           # BSD disklabel
   options         GEOM_PART_BSD64         # BSD disklabel64
   options         GEOM_PART_EBR           # Extended Boot Records
   options         GEOM_PART_GPT           # GPT partitioning
   options         GEOM_PART_LDM           # Logical Disk Manager
   options         GEOM_PART_MBR           # MBR partitioning
   options         GEOM_PART_VTOC8         # SMI VTOC8 disk label
   options         GEOM_RAID               # Soft RAID functionality.
   options         GEOM_RAID3              # RAID3 functionality.
   options         GEOM_SHSEC              # Shared secret.
   options         GEOM_STRIPE             # Disk striping.
   options         GEOM_UZIP               # Read-only compressed disks
   options         GEOM_VINUM              # Vinum logical volume manager
   options         GEOM_VIRSTOR            # Virtual storage.
   options         GEOM_ZERO               # Performance testing helper.
   
   #
   # The root device and filesystem type can be compiled in;
   # this provides a fallback option if the root device cannot
   # be correctly guessed by the bootstrap code, or an override if
   # the RB_DFLTROOT flag (-r) is specified when booting the kernel.
   #
   options         ROOTDEVNAME=\"ufs:da0s2e\"
   
   
   #####################################################################
   # Scheduler options:
   #
   # Specifying one of SCHED_4BSD or SCHED_ULE is mandatory.  These options
   # select which scheduler is compiled in.
   #
   # SCHED_4BSD is the historical, proven, BSD scheduler.  It has a global run
   # queue and no CPU affinity which makes it suboptimal for SMP.  It has very
   # good interactivity and priority selection.
   #
   # SCHED_ULE provides significant performance advantages over 4BSD on many
   # workloads on SMP machines.  It supports cpu-affinity, per-cpu runqueues
   # and scheduler locks.  It also has a stronger notion of interactivity 
   # which leads to better responsiveness even on uniprocessor machines.  This
   # is the default scheduler.
   #
   # SCHED_STATS is a debugging option which keeps some stats in the sysctl
   # tree at 'kern.sched.stats' and is useful for debugging scheduling decisions.
   #
   options         SCHED_4BSD
   options         SCHED_STATS
   #options        SCHED_ULE
   
   #####################################################################
   # SMP OPTIONS:
   #
   # SMP enables building of a Symmetric MultiProcessor Kernel.
   
   # Mandatory:
   options         SMP                     # Symmetric MultiProcessor Kernel
   
   # EARLY_AP_STARTUP releases the Application Processors earlier in the
   # kernel startup process (before devices are probed) rather than at the
   # end.  This is a temporary option for use during the transition from
   # late to early AP startup.
   options         EARLY_AP_STARTUP
   
   # MAXCPU defines the maximum number of CPUs that can boot in the system.
   # A default value should be already present, for every architecture.
   options         MAXCPU=32
   
   # NUMA enables use of Non-Uniform Memory Access policies in various kernel
   # subsystems.
   options         NUMA
   
   # MAXMEMDOM defines the maximum number of memory domains that can boot in the
   # system.  A default value should already be defined by every architecture.
   options         MAXMEMDOM=2
   
   # ADAPTIVE_MUTEXES changes the behavior of blocking mutexes to spin
   # if the thread that currently owns the mutex is executing on another
   # CPU.  This behavior is enabled by default, so this option can be used
   # to disable it.
   options         NO_ADAPTIVE_MUTEXES
   
   # ADAPTIVE_RWLOCKS changes the behavior of reader/writer locks to spin
   # if the thread that currently owns the rwlock is executing on another
   # CPU.  This behavior is enabled by default, so this option can be used
   # to disable it.
   options         NO_ADAPTIVE_RWLOCKS
   
   # ADAPTIVE_SX changes the behavior of sx locks to spin if the thread that
   # currently owns the sx lock is executing on another CPU.
   # This behavior is enabled by default, so this option can be used to
   # disable it.
   options         NO_ADAPTIVE_SX
   
   # MUTEX_NOINLINE forces mutex operations to call functions to perform each
   # operation rather than inlining the simple cases.  This can be used to
   # shrink the size of the kernel text segment.  Note that this behavior is
   # already implied by the INVARIANT_SUPPORT, INVARIANTS, KTR, LOCK_PROFILING,
   # and WITNESS options.
   options         MUTEX_NOINLINE
   
   # RWLOCK_NOINLINE forces rwlock operations to call functions to perform each
   # operation rather than inlining the simple cases.  This can be used to
   # shrink the size of the kernel text segment.  Note that this behavior is
   # already implied by the INVARIANT_SUPPORT, INVARIANTS, KTR, LOCK_PROFILING,
   # and WITNESS options.
   options         RWLOCK_NOINLINE
   
   # SX_NOINLINE forces sx lock operations to call functions to perform each
   # operation rather than inlining the simple cases.  This can be used to
   # shrink the size of the kernel text segment.  Note that this behavior is
   # already implied by the INVARIANT_SUPPORT, INVARIANTS, KTR, LOCK_PROFILING,
   # and WITNESS options.
   options         SX_NOINLINE
   
   # SMP Debugging Options:
   #
   # CALLOUT_PROFILING enables rudimentary profiling of the callwheel data
   #         structure used as backend in callout(9).
   # PREEMPTION allows the threads that are in the kernel to be preempted by
   #         higher priority [interrupt] threads.  It helps with interactivity
   #         and allows interrupt threads to run sooner rather than waiting.
   # FULL_PREEMPTION instructs the kernel to preempt non-realtime kernel
   #         threads.  Its sole use is to expose race conditions and other
   #         bugs during development.  Enabling this option will reduce
   #         performance and increase the frequency of kernel panics by
   #         design.  If you aren't sure that you need it then you don't.
   #         Relies on the PREEMPTION option.  DON'T TURN THIS ON.
   # SLEEPQUEUE_PROFILING enables rudimentary profiling of the hash table
   #         used to hold active sleep queues as well as sleep wait message
   #         frequency.
   # TURNSTILE_PROFILING enables rudimentary profiling of the hash table
   #         used to hold active lock queues.
   # UMTX_PROFILING enables rudimentary profiling of the hash table used 
   #         to hold active lock queues.
   # WITNESS enables the witness code which detects deadlocks and cycles
   #         during locking operations.
   # WITNESS_KDB causes the witness code to drop into the kernel debugger if
   #         a lock hierarchy violation occurs or if locks are held when going to
   #         sleep.
   # WITNESS_SKIPSPIN disables the witness checks on spin mutexes.
   options         PREEMPTION
   options         FULL_PREEMPTION
   options         WITNESS
   options         WITNESS_KDB
   options         WITNESS_SKIPSPIN
   
   # LOCK_PROFILING - Profiling locks.  See LOCK_PROFILING(9) for details.
   options         LOCK_PROFILING
   # Set the number of buffers and the hash size.  The hash size MUST be larger
   # than the number of buffers.  Hash size should be prime.
   options         MPROF_BUFFERS="1536"
   options         MPROF_HASH_SIZE="1543"
   
   # Profiling for the callout(9) backend.
   options         CALLOUT_PROFILING
   
   # Profiling for internal hash tables.
   options         SLEEPQUEUE_PROFILING
   options         TURNSTILE_PROFILING
   options         UMTX_PROFILING
   
   # Debugging traces for epoch(9) misuse
   options         EPOCH_TRACE
   
   #####################################################################
   # COMPATIBILITY OPTIONS
   
   # Old tty interface.
   options         COMPAT_43TTY
   
   # Note that as a general rule, COMPAT_FREEBSD<n> depends on
   # COMPAT_FREEBSD<n+1>, COMPAT_FREEBSD<n+2>, etc.
   
   # Enable FreeBSD4 compatibility syscalls
   options         COMPAT_FREEBSD4
   
   # Enable FreeBSD5 compatibility syscalls
   options         COMPAT_FREEBSD5
   
   # Enable FreeBSD6 compatibility syscalls
   options         COMPAT_FREEBSD6
   
   # Enable FreeBSD7 compatibility syscalls
   options         COMPAT_FREEBSD7
   
   # Enable FreeBSD9 compatibility syscalls
   options         COMPAT_FREEBSD9
   
   # Enable FreeBSD10 compatibility syscalls
   options         COMPAT_FREEBSD10
   
   # Enable FreeBSD11 compatibility syscalls
   options         COMPAT_FREEBSD11
   
   # Enable FreeBSD12 compatibility syscalls
   options         COMPAT_FREEBSD12
   
   # Enable FreeBSD13 compatibility syscalls
   options         COMPAT_FREEBSD13
   
   # Enable Linux Kernel Programming Interface
   options         COMPAT_LINUXKPI
   
   #
   # These three options provide support for System V Interface
   # Definition-style interprocess communication, in the form of shared
   # memory, semaphores, and message queues, respectively.
   #
   options         SYSVSHM
   options         SYSVSEM
   options         SYSVMSG
   
   
   #####################################################################
   # DEBUGGING OPTIONS
   
   #
   # Compile with kernel debugger related code.
   #
   options         KDB
   
   #
   # Print a stack trace of the current thread on the console for a panic.
   #
   options         KDB_TRACE
   
   #
   # Don't enter the debugger for a panic. Intended for unattended operation
   # where you may want to enter the debugger from the console, but still want
   # the machine to recover from a panic.
   #
   options         KDB_UNATTENDED
   
   #
   # Enable the ddb debugger backend.
   #
   options         DDB
   
   #
   # Print the numerical value of symbols in addition to the symbolic
   # representation.
   #
   options         DDB_NUMSYM
   
   #
   # Enable the remote gdb debugger backend.
   #
   options         GDB
   
   #
   # Trashes list pointers when they become invalid (i.e., the element is
   # removed from a list).  Relatively inexpensive to enable.
   #
   options         QUEUE_MACRO_DEBUG_TRASH
   
   #
   # Stores information about the last caller to modify the list object
   # in the list object.  Requires additional memory overhead.
   #
   #options        QUEUE_MACRO_DEBUG_TRACE
   
   #
   # SYSCTL_DEBUG enables a 'sysctl' debug tree that can be used to dump the
   # contents of the registered sysctl nodes on the console.  It is disabled by
   # default because it generates excessively verbose console output that can
   # interfere with serial console operation.
   #
   options         SYSCTL_DEBUG
   
   #
   # Enable textdump by default, this disables kernel core dumps.
   #
   options         TEXTDUMP_PREFERRED
   
   #
   # Enable extra debug messages while performing textdumps.
   #
   options         TEXTDUMP_VERBOSE
   
   #
   # NO_SYSCTL_DESCR omits the sysctl node descriptions to save space in the
   # resulting kernel.
   options         NO_SYSCTL_DESCR
   
   #
   # MALLOC_DEBUG_MAXZONES enables multiple uma zones for malloc(9)
   # allocations that are smaller than a page.  The purpose is to isolate
   # different malloc types into hash classes, so that any buffer
   # overruns or use-after-free will usually only affect memory from
   # malloc types in that hash class.  This is purely a debugging tool;
   # by varying the hash function and tracking which hash class was
   # corrupted, the intersection of the hash classes from each instance
   # will point to a single malloc type that is being misused.  At this
   # point inspection or memguard(9) can be used to catch the offending
   # code.
   #
   options         MALLOC_DEBUG_MAXZONES=8
   
   #
   # DEBUG_MEMGUARD builds and enables memguard(9), a replacement allocator
   # for the kernel used to detect modify-after-free scenarios.  See the
   # memguard(9) man page for more information on usage.
   #
   options         DEBUG_MEMGUARD
   
   #
   # DEBUG_REDZONE enables buffer underflows and buffer overflows detection for
   # malloc(9).
   #
   options         DEBUG_REDZONE
   
   #
   # EARLY_PRINTF enables support for calling a special printf (eprintf)
   # very early in the kernel (before cn_init() has been called).  This
   # should only be used for debugging purposes early in boot.  Normally,
   # it is not defined.  It is commented out here because this feature
   # isn't generally available. And the required eputc() isn't defined.
   #
   #options        EARLY_PRINTF
   
   #
   # KTRACE enables the system-call tracing facility ktrace(2).  To be more
   # SMP-friendly, KTRACE uses a worker thread to process most trace events
   # asynchronously to the thread generating the event.  This requires a
   # pre-allocated store of objects representing trace events.  The
   # KTRACE_REQUEST_POOL option specifies the initial size of this store.
   # The size of the pool can be adjusted both at boottime and runtime via
   # the kern.ktrace_request_pool tunable and sysctl.
   #
   options         KTRACE                  #kernel tracing
   options         KTRACE_REQUEST_POOL=101
   
   #
   # KTR is a kernel tracing facility imported from BSD/OS.  It is
   # enabled with the KTR option.  KTR_ENTRIES defines the number of
   # entries in the circular trace buffer; it may be an arbitrary number.
   # KTR_BOOT_ENTRIES defines the number of entries during the early boot,
   # before malloc(9) is functional.
   # KTR_COMPILE defines the mask of events to compile into the kernel as
   # defined by the KTR_* constants in <sys/ktr.h>.  KTR_MASK defines the
   # initial value of the ktr_mask variable which determines at runtime
   # what events to trace.  KTR_CPUMASK determines which CPU's log
   # events, with bit X corresponding to CPU X.  The layout of the string
   # passed as KTR_CPUMASK must match a series of bitmasks each of them
   # separated by the "," character (ie:
   # KTR_CPUMASK=0xAF,0xFFFFFFFFFFFFFFFF).  KTR_VERBOSE enables
   # dumping of KTR events to the console by default.  This functionality
   # can be toggled via the debug.ktr_verbose sysctl and defaults to off
   # if KTR_VERBOSE is not defined.  See ktr(4) and ktrdump(8) for details.
   #
   options         KTR
   options         KTR_BOOT_ENTRIES=1024
   options         KTR_ENTRIES=(128*1024)
   options         KTR_COMPILE=(KTR_ALL)
   options         KTR_MASK=KTR_INTR
   options         KTR_CPUMASK=0x3
   options         KTR_VERBOSE
   
   #
   # ALQ(9) is a facility for the asynchronous queuing of records from the kernel
   # to a vnode, and is employed by services such as ktr(4) to produce trace
   # files based on a kernel event stream.  Records are written asynchronously
   # in a worker thread.
   #
   options         ALQ
   options         KTR_ALQ
   
   #
   # The INVARIANTS option is used in a number of source files to enable
   # extra sanity checking of internal structures.  This support is not
   # enabled by default because of the extra time it would take to check
   # for these conditions, which can only occur as a result of
   # programming errors.
   #
   options         INVARIANTS
   
   #
   # The INVARIANT_SUPPORT option makes us compile in support for
   # verifying some of the internal structures.  It is a prerequisite for
   # 'INVARIANTS', as enabling 'INVARIANTS' will make these functions be
   # called.  The intent is that you can set 'INVARIANTS' for single
   # source files (by changing the source file or specifying it on the
   # command line) if you have 'INVARIANT_SUPPORT' enabled.  Also, if you
   # wish to build a kernel module with 'INVARIANTS', then adding
   # 'INVARIANT_SUPPORT' to your kernel will provide all the necessary
   # infrastructure without the added overhead.
   #
   options         INVARIANT_SUPPORT
   
   #
   # The KASSERT_PANIC_OPTIONAL option allows kasserts to fire without
   # necessarily inducing a panic.  Panic is the default behavior, but
   # runtime options can configure it either entirely off, or off with a
   # limit.
   #
   options         KASSERT_PANIC_OPTIONAL
   
   #
   # The DIAGNOSTIC option is used to enable extra debugging information
   # and invariants checking.  The added checks are too expensive or noisy
   # for an INVARIANTS kernel and thus are disabled by default.  It is
   # expected that a kernel configured with DIAGNOSTIC will also have the
   # INVARIANTS option enabled.
   #
   options         DIAGNOSTIC
   
   #
   # REGRESSION causes optional kernel interfaces necessary only for regression
   # testing to be enabled.  These interfaces may constitute security risks
   # when enabled, as they permit processes to easily modify aspects of the
   # run-time environment to reproduce unlikely or unusual (possibly normally
   # impossible) scenarios.
   #
   options         REGRESSION
   
   #
   # This option lets some drivers co-exist that can't co-exist in a running
   # system.  This is used to be able to compile all kernel code in one go for
   # quality assurance purposes (like this file, which the option takes it name
   # from.)
   #
   options         COMPILING_LINT
   
   #
   # STACK enables the stack(9) facility, allowing the capture of kernel stack
   # for the purpose of procinfo(1), etc.  stack(9) will also be compiled in
   # automatically if DDB(4) is compiled into the kernel.
   #
   options         STACK
   
   #
   # The NUM_CORE_FILES option specifies the limit for the number of core
   # files generated by a particular process, when the core file format
   # specifier includes the %I pattern. Since we only have 1 character for
   # the core count in the format string, meaning the range will be 0-9, the
   # maximum value allowed for this option is 10.
   # This core file limit can be adjusted at runtime via the debug.ncores
   # sysctl.
   #
   options         NUM_CORE_FILES=5
   
   #
   # The TSLOG option enables timestamped logging of events, especially
   # function entries/exits, in order to track the time spent by the kernel.
   # In particular, this is useful when investigating the early boot process,
   # before it is possible to use more sophisticated tools like DTrace.
   # The TSLOGSIZE option controls the size of the (preallocated, fixed
   # length) buffer used for storing these events (default: 262144 records).
   #
   # For security reasons the TSLOG option should not be enabled on systems
   # used in production.
   #
   options         TSLOG
   options         TSLOGSIZE=262144
   
   
   #####################################################################
   # PERFORMANCE MONITORING OPTIONS
   
   #
   # The hwpmc driver that allows the use of in-CPU performance monitoring
   # counters for performance monitoring.  The base kernel needs to be configured
   # with the 'options' line, while the hwpmc device can be either compiled
   # in or loaded as a loadable kernel module.
   #
   # Additional configuration options may be required on specific architectures,
   # please see hwpmc(4).
   
   device          hwpmc                   # Driver (also a loadable module)
   options         HWPMC_DEBUG
   options         HWPMC_HOOKS             # Other necessary kernel hooks
   
   
   #####################################################################
   # NETWORKING OPTIONS
   
   #
   # Protocol families
   #
   options         INET                    #Internet communications protocols
   options         INET6                   #IPv6 communications protocols
   #
   # Note if you include INET/INET6 or both options
   # You *must* define at least one of the congestion control
   # options or the compile will fail. GENERIC defines
   # options CC_CUBIC. You may want to specify a default
   # if multiple congestion controls are compiled in.
   # The string in default is the name of the
   # cc module as it would appear in the sysctl for
   # setting the default. The code defines CUBIC
   # as default, or the sole cc_module compiled in.
   #
   options         CC_CDG
   options         CC_CHD
   options         CC_CUBIC
   options         CC_DCTCP
   options         CC_HD
   options         CC_HTCP
   options         CC_NEWRENO
   options         CC_VEGAS
   options         CC_DEFAULT=\"cubic\"
   options         RATELIMIT               # TX rate limiting support
   
   options         ROUTETABLES=2           # allocated fibs up to 65536. default is 1.
                                           # but that would be a bad idea as they are large.
   
   options         TCP_OFFLOAD             # TCP offload support.
   options         TCP_RFC7413             # TCP Fast Open
   
   options         TCPHPTS
   makeoptions     WITH_EXTRA_TCP_STACKS=1 # RACK and BBR TCP kernel modules
   
   # In order to enable IPSEC you MUST also add device crypto to 
   # your kernel configuration
   options         IPSEC                   #IP security (requires device crypto)
   
   # Option IPSEC_SUPPORT does not enable IPsec, but makes it possible to 
   # load it as a kernel module. You still MUST add device crypto to your kernel
   # configuration.
   options         IPSEC_SUPPORT
   #options        IPSEC_DEBUG             #debug for IP security
   
   
   # TLS framing and encryption/decryption of data over TCP sockets.
   options         KERN_TLS                # TLS transmit and receive offload
   
   # Netlink kernel/user<>kernel/user messaging interface
   options         NETLINK
   
   #
   # SMB/CIFS requester
   # NETSMB enables support for SMB protocol, it requires LIBMCHAIN and LIBICONV
   # options.
   options         NETSMB                  #SMB/CIFS requester
   
   # mchain library. It can be either loaded as KLD or compiled into kernel
   options         LIBMCHAIN
   
   # libalias library, performing NAT
   options         LIBALIAS
   
   #
   # SCTP is a NEW transport protocol defined by
   # RFC2960 updated by RFC3309 and RFC3758.. and
   # soon to have a new base RFC and many many more
   # extensions. This release supports all the extensions
   # including many drafts (most about to become RFC's).
   # It is the reference implementation of SCTP
   # and is quite well tested.
   #
   # Note YOU MUST have both INET and INET6 defined.
   # You don't have to enable V6, but SCTP is 
   # dual stacked and so far we have not torn apart
   # the V6 and V4.. since an association can span
   # both a V6 and V4 address at the SAME time :-)
   #
   # The SCTP_SUPPORT option does not enable SCTP, but provides the necessary
   # support for loading SCTP as a loadable kernel module.
   #
   options         SCTP
   options         SCTP_SUPPORT
   
   # There are bunches of options:
   # this one turns on all sorts of
   # nastily printing that you can
   # do. It's all controlled by a
   # bit mask (settable by socket opt and
   # by sysctl). Including will not cause
   # logging until you set the bits.. but it
   # can be quite verbose.. so without this
   # option we don't do any of the tests for
   # bits and prints.. which makes the code run
   # faster.. if you are not debugging don't use.
   options         SCTP_DEBUG
   
   #
   # All that options after that turn on specific types of
   # logging. You can monitor CWND growth, flight size
   # and all sorts of things. Go look at the code and
   # see. I have used this to produce interesting 
   # charts and graphs as well :->
   # 
   # I have not yet committed the tools to get and print
   # the logs, I will do that eventually .. before then
   # if you want them send me an email rrs@freebsd.org
   # You basically must have ktr(4) enabled for these
   # and you then set the sysctl to turn on/off various
   # logging bits. Use ktrdump(8) to pull the log and run
   # it through a display program.. and graphs and other
   # things too.
   #
   options         SCTP_LOCK_LOGGING
   options         SCTP_MBUF_LOGGING
   options         SCTP_MBCNT_LOGGING
   options         SCTP_PACKET_LOGGING
   options         SCTP_LTRACE_CHUNKS
   options         SCTP_LTRACE_ERRORS
   
   # altq(9). Enable the base part of the hooks with the ALTQ option.
   # Individual disciplines must be built into the base system and can not be
   # loaded as modules at this point. ALTQ requires a stable TSC so if yours is
   # broken or changes with CPU throttling then you must also have the ALTQ_NOPCC
   # option.
   options         ALTQ
   options         ALTQ_CBQ        # Class Based Queueing
   options         ALTQ_RED        # Random Early Detection
   options         ALTQ_RIO        # RED In/Out
   options         ALTQ_CODEL      # CoDel Active Queueing
   options         ALTQ_HFSC       # Hierarchical Packet Scheduler
   options         ALTQ_FAIRQ      # Fair Packet Scheduler
   options         ALTQ_CDNR       # Traffic conditioner
   options         ALTQ_PRIQ       # Priority Queueing
   options         ALTQ_NOPCC      # Required if the TSC is unusable
   options         ALTQ_DEBUG
   
   # netgraph(4). Enable the base netgraph code with the NETGRAPH option.
   # Individual node types can be enabled with the corresponding option
   # listed below; however, this is not strictly necessary as netgraph
   # will automatically load the corresponding KLD module if the node type
   # is not already compiled into the kernel. Each type below has a
   # corresponding man page, e.g., ng_async(8).
   options         NETGRAPH                # netgraph(4) system
   options         NETGRAPH_DEBUG          # enable extra debugging, this
                                           # affects netgraph(4) and nodes
   # Node types
   options         NETGRAPH_ASYNC
   options         NETGRAPH_ATMLLC
   options         NETGRAPH_ATM_ATMPIF
   options         NETGRAPH_BLUETOOTH              # ng_bluetooth(4)
   options         NETGRAPH_BLUETOOTH_HCI          # ng_hci(4)
   options         NETGRAPH_BLUETOOTH_L2CAP        # ng_l2cap(4)
   options         NETGRAPH_BLUETOOTH_SOCKET       # ng_btsocket(4)
   options         NETGRAPH_BLUETOOTH_UBT          # ng_ubt(4)
   options         NETGRAPH_BLUETOOTH_UBTBCMFW     # ubtbcmfw(4)
   options         NETGRAPH_BPF
   options         NETGRAPH_BRIDGE
   options         NETGRAPH_CAR
   options         NETGRAPH_CHECKSUM
   options         NETGRAPH_CISCO
   options         NETGRAPH_DEFLATE
   options         NETGRAPH_DEVICE
   options         NETGRAPH_ECHO
   options         NETGRAPH_EIFACE
   options         NETGRAPH_ETHER
   options         NETGRAPH_FRAME_RELAY
   options         NETGRAPH_GIF
   options         NETGRAPH_GIF_DEMUX
   options         NETGRAPH_HOLE
   options         NETGRAPH_IFACE
   options         NETGRAPH_IP_INPUT
   options         NETGRAPH_IPFW
   options         NETGRAPH_KSOCKET
   options         NETGRAPH_L2TP
   options         NETGRAPH_LMI
   options         NETGRAPH_MPPC_COMPRESSION
   options         NETGRAPH_MPPC_ENCRYPTION
   options         NETGRAPH_NETFLOW
   options         NETGRAPH_NAT
   options         NETGRAPH_ONE2MANY
   options         NETGRAPH_PATCH
   options         NETGRAPH_PIPE
   options         NETGRAPH_PPP
   options         NETGRAPH_PPPOE
   options         NETGRAPH_PPTPGRE
   options         NETGRAPH_PRED1
   options         NETGRAPH_RFC1490
   options         NETGRAPH_SOCKET
   options         NETGRAPH_SPLIT
   options         NETGRAPH_TAG
   options         NETGRAPH_TCPMSS
   options         NETGRAPH_TEE
   options         NETGRAPH_UI
   options         NETGRAPH_VJC
   options         NETGRAPH_VLAN
   
   # NgATM - Netgraph ATM
   options         NGATM_ATM
   options         NGATM_ATMBASE
   options         NGATM_SSCOP
   options         NGATM_SSCFU
   options         NGATM_UNI
   options         NGATM_CCATM
   
   # Network stack virtualization.
   options VIMAGE
   options VNET_DEBUG      # debug for VIMAGE
   
   #
   # Network interfaces:
   #  The `loop' device is MANDATORY when networking is enabled.
   device          loop
   
   #  The `ether' device provides generic code to handle
   #  Ethernets; it is MANDATORY when an Ethernet device driver is
   #  configured.
   device          ether
   
   #  The `vlan' device implements the VLAN tagging of Ethernet frames
   #  according to IEEE 802.1Q.
   device          vlan
   
   # The `vxlan' device implements the VXLAN encapsulation of Ethernet
   # frames in UDP packets according to RFC7348.
   device          vxlan
   
   #  The `wlan' device provides generic code to support 802.11
   #  drivers, including host AP mode; it is MANDATORY for the wi,
   #  and ath drivers and will eventually be required by all 802.11 drivers.
   device          wlan
   options         IEEE80211_DEBUG         #enable debugging msgs
   options         IEEE80211_SUPPORT_MESH  #enable 802.11s D3.0 support
   options         IEEE80211_SUPPORT_TDMA  #enable TDMA support
   
   #  The `wlan_wep', `wlan_tkip', and `wlan_ccmp' devices provide
   #  support for WEP, TKIP, and AES-CCMP crypto protocols optionally
   #  used with 802.11 devices that depend on the `wlan' module.
   device          wlan_wep
   device          wlan_ccmp
   device          wlan_tkip
   
   #  The `wlan_xauth' device provides support for external (i.e. user-mode)
   #  authenticators for use with 802.11 drivers that use the `wlan'
   #  module and support 802.1x and/or WPA security protocols.
   device          wlan_xauth
   
   #  The `wlan_acl' device provides a MAC-based access control mechanism
   #  for use with 802.11 drivers operating in ap mode and using the
   #  `wlan' module.
   #  The 'wlan_amrr' device provides AMRR transmit rate control algorithm
   device          wlan_acl
   device          wlan_amrr
   
   #  The `bpf' device enables the Berkeley Packet Filter.  Be
   #  aware of the legal and administrative consequences of enabling this
   #  option.  DHCP requires bpf.
   device          bpf
   
   #  The `netmap' device implements memory-mapped access to network
   #  devices from userspace, enabling wire-speed packet capture and
   #  generation even at 10Gbit/s. Requires support in the device
   #  driver. Supported drivers are ixgbe, e1000, re.
   device          netmap
   
   #  The `disc' device implements a minimal network interface,
   #  which throws away all packets sent and never receives any.  It is
   #  included for testing and benchmarking purposes.
   device          disc
   
   # The `epair' device implements a virtual back-to-back connected Ethernet
   # like interface pair.
   device          epair
   
   #  The `edsc' device implements a minimal Ethernet interface,
   #  which discards all packets sent and receives none.
   device          edsc
   
   #  The `tuntap' device implements (user-)ppp, nos-tun(8) and a pty-like virtual
   #  Ethernet interface
   device          tuntap
   
   #  The `gif' device implements IPv6 over IP4 tunneling,
   #  IPv4 over IPv6 tunneling, IPv4 over IPv4 tunneling and
   #  IPv6 over IPv6 tunneling.
   #  The `gre' device implements GRE (Generic Routing Encapsulation) tunneling,
   #  as specified in the RFC 2784 and RFC 2890.
   #  The `me' device implements Minimal Encapsulation within IPv4 as
   #  specified in the RFC 2004.
   #  The XBONEHACK option allows the same pair of addresses to be configured on
   #  multiple gif interfaces.
   device          gif
   device          gre
   device          me
   options         XBONEHACK
   
   #  The `stf' device implements 6to4 encapsulation.
   device          stf
   
   # The pf packet filter consists of three devices:
   #  The `pf' device provides /dev/pf and the firewall code itself.
   #  The `pflog' device provides the pflog0 interface which logs packets.
   #  The `pfsync' device provides the pfsync0 interface used for
   #   synchronization of firewall state tables (over the net).
   device          pf
   device          pflog
   device          pfsync
   
   # Bridge interface.
   device          if_bridge
   
   # Common Address Redundancy Protocol. See carp(4) for more details.
   device          carp
   
   # IPsec interface.
   device          enc
   
   # Link aggregation interface.
   device          lagg
   
   # WireGuard interface.
   device          wg
   
   #
   # Internet family options:
   #
   # MROUTING enables the kernel multicast packet forwarder, which works
   # with mrouted and XORP.
   #
   # IPFIREWALL enables support for IP firewall construction, in
   # conjunction with the `ipfw' program.  IPFIREWALL_VERBOSE sends
   # logged packets to the system logger.  IPFIREWALL_VERBOSE_LIMIT
   # limits the number of times a matching entry can be logged.
   #
   # WARNING:  IPFIREWALL defaults to a policy of "deny ip from any to any"
   # and if you do not add other rules during startup to allow access,
   # YOU WILL LOCK YOURSELF OUT.  It is suggested that you set firewall_type=open
   # in /etc/rc.conf when first enabling this feature, then refining the
   # firewall rules in /etc/rc.firewall after you've tested that the new kernel
   # feature works properly.
   #
   # IPFIREWALL_DEFAULT_TO_ACCEPT causes the default rule (at boot) to
   # allow everything.  Use with care, if a cracker can crash your
   # firewall machine, they can get to your protected machines.  However,
   # if you are using it as an as-needed filter for specific problems as
   # they arise, then this may be for you.  Changing the default to 'allow'
   # means that you won't get stuck if the kernel and /sbin/ipfw binary get
   # out of sync.
   #
   # IPDIVERT enables the divert IP sockets, used by ``ipfw divert''.  It
   # depends on IPFIREWALL if compiled into the kernel.
   #
  # IPFIREWALL_NAT adds support for in kernel nat in ipfw, and it requires
  # LIBALIAS.
  #
  # IPFIREWALL_NAT64 adds support for in kernel NAT64 in ipfw.
  #
  # IPFIREWALL_NPTV6 adds support for in kernel NPTv6 in ipfw.
  #
  # IPFIREWALL_PMOD adds support for protocols modification module. Currently
  # it supports only TCP MSS modification.
  #
  # IPSTEALTH enables code to support stealth forwarding (i.e., forwarding
  # packets without touching the TTL).  This can be useful to hide firewalls
  # from traceroute and similar tools.
  #
  # PF_DEFAULT_TO_DROP causes the default pf(4) rule to deny everything.
  #
  # TCPPCAP enables code which keeps the last n packets sent and received
  # on a TCP socket.
  #
  # TCP_BLACKBOX enables enhanced TCP event logging.
  #
  # TCP_HHOOK enables the hhook(9) framework hooks for the TCP stack.
  #
  # ROUTE_MPATH provides support for multipath routing.
  #
  options         MROUTING                # Multicast routing
  options         IPFIREWALL              #firewall
  options         IPFIREWALL_VERBOSE      #enable logging to syslogd(8)
  options         IPFIREWALL_VERBOSE_LIMIT=100    #limit verbosity
  options         IPFIREWALL_DEFAULT_TO_ACCEPT    #allow everything by default
  options         IPFIREWALL_NAT          #ipfw kernel nat support
  options         IPFIREWALL_NAT64        #ipfw kernel NAT64 support
  options         IPFIREWALL_NPTV6        #ipfw kernel IPv6 NPT support
  options         IPDIVERT                #divert sockets
  options         IPFILTER                #ipfilter support
  options         IPFILTER_LOG            #ipfilter logging
  options         IPFILTER_LOOKUP         #ipfilter pools
  options         IPFILTER_DEFAULT_BLOCK  #block all packets by default
  options         IPSTEALTH               #support for stealth forwarding
  options         PF_DEFAULT_TO_DROP      #drop everything by default
  options         TCPPCAP
  options         TCP_BLACKBOX
  options         TCP_HHOOK
  options         ROUTE_MPATH
  
  # The MBUF_STRESS_TEST option enables options which create
  # various random failures / extreme cases related to mbuf
  # functions.  See mbuf(9) for a list of available test cases.
  # MBUF_PROFILING enables code to profile the mbuf chains
  # exiting the system (via participating interfaces) and
  # return a logarithmic histogram of monitored parameters
  # (e.g. packet size, wasted space, number of mbufs in chain).
  options         MBUF_STRESS_TEST
  options         MBUF_PROFILING
  
  # Statically link in accept filters
  options         ACCEPT_FILTER_DATA
  options         ACCEPT_FILTER_DNS
  options         ACCEPT_FILTER_HTTP
  
  # TCP_SIGNATURE adds support for RFC 2385 (TCP-MD5) digests. These are
  # carried in TCP option 19. This option is commonly used to protect
  # TCP sessions (e.g. BGP) where IPSEC is not available nor desirable.
  # This is enabled on a per-socket basis using the TCP_MD5SIG socket option.
  # This requires the use of 'device crypto' and either 'options IPSEC' or
  # 'options IPSEC_SUPPORT'.
  options         TCP_SIGNATURE           #include support for RFC 2385
  
  # DUMMYNET enables the "dummynet" bandwidth limiter.  You need IPFIREWALL
  # as well.  See dummynet(4) and ipfw(8) for more info.  When you run
  # DUMMYNET, HZ/kern.hz should be at least 1000 for adequate response.
  options         DUMMYNET
  
  # The DEBUGNET option enables a basic debug/panic-time networking API.  It
  # is used by NETDUMP and NETGDB.
  options         DEBUGNET
  
  # The NETDUMP option enables netdump(4) client support in the kernel.
  # This allows a panicking kernel to transmit a kernel dump to a remote host.
  options         NETDUMP
  
  # The NETGDB option enables netgdb(4) support in the kernel.  This allows a
  # panicking kernel to be debugged as a GDB remote over the network.
  options         NETGDB
  
  #####################################################################
  # FILESYSTEM OPTIONS
  
  #
  # Only the root filesystem needs to be statically compiled or preloaded
  # as module; everything else will be automatically loaded at mount
  # time.  Some people still prefer to statically compile other
  # filesystems as well.
  #
  # NB: The UNION filesystem was known to be buggy in the past.  It is now
  # being actively maintained, although there are still some issues being
  # resolved.
  #
  
  # One of these is mandatory:
  options         FFS                     #Fast filesystem
  options         NFSCL                   #Network File System client
  
  # The rest are optional:
  options         AUTOFS                  #Automounter filesystem
  options         CD9660                  #ISO 9660 filesystem
  options         FDESCFS                 #File descriptor filesystem
  options         FUSEFS                  #FUSEFS support module
  options         MSDOSFS                 #MS DOS File System (FAT, FAT32)
  options         NFSLOCKD                #Network Lock Manager
  options         NFSD                    #Network Filesystem Server
  options         KGSSAPI                 #Kernel GSSAPI implementation
  
  options         NULLFS                  #NULL filesystem
  options         PROCFS                  #Process filesystem (requires PSEUDOFS)
  options         PSEUDOFS                #Pseudo-filesystem framework
  options         PSEUDOFS_TRACE          #Debugging support for PSEUDOFS
  options         SMBFS                   #SMB/CIFS filesystem
  options         TMPFS                   #Efficient memory filesystem
  options         UDF                     #Universal Disk Format
  options         UNIONFS                 #Union filesystem
  # The xFS_ROOT options REQUIRE the associated ``options xFS''
  options         NFS_ROOT                #NFS usable as root device
  
  # Soft updates is a technique for improving filesystem speed and
  # making abrupt shutdown less risky.
  #
  options         SOFTUPDATES
  
  # Extended attributes allow additional data to be associated with files,
  # and is used for ACLs, Capabilities, and MAC labels.
  # See src/sys/ufs/ufs/README.extattr for more information.
  options         UFS_EXTATTR
  options         UFS_EXTATTR_AUTOSTART
  
  # Access Control List support for UFS filesystems.  The current ACL
  # implementation requires extended attribute support, UFS_EXTATTR,
  # for the underlying filesystem.
  # See src/sys/ufs/ufs/README.acls for more information.
  options         UFS_ACL
  
  # Directory hashing improves the speed of operations on very large
  # directories at the expense of some memory.
  options         UFS_DIRHASH
  
  # Gjournal-based UFS journaling support.
  options         UFS_GJOURNAL
  
  # Make space in the kernel for a root filesystem on a md device.
  # Define to the number of kilobytes to reserve for the filesystem.
  # This is now optional.
  # If not defined, the root filesystem passed in as the MFS_IMAGE makeoption
  # will be automatically embedded in the kernel during linking. Its exact size
  # will be consumed within the kernel.
  # If defined, the old way of embedding the filesystem in the kernel will be
  # used. That is to say MD_ROOT_SIZE KB will be allocated in the kernel and
  # later, the filesystem image passed in as the MFS_IMAGE makeoption will be
  # dd'd into the reserved space if it fits.
  options         MD_ROOT_SIZE=10
  
  # Make the md device a potential root device, either with preloaded
  # images of type mfs_root or md_root.
  options         MD_ROOT
  
  # Write-protect the md root device so that it may not be mounted writeable.
  options         MD_ROOT_READONLY
  
  # Allow to read MD image from external memory regions
  options         MD_ROOT_MEM
  
  # Disk quotas are supported when this option is enabled.
  options         QUOTA                   #enable disk quotas
  
  # If you are running a machine just as a fileserver for PC and MAC
  # users, using SAMBA, you may consider setting this option
  # and keeping all those users' directories on a filesystem that is
  # mounted with the suiddir option. This gives new files the same
  # ownership as the directory (similar to group). It's a security hole
  # if you let these users run programs, so confine it to file-servers
  # (but it'll save you lots of headaches in those cases). Root owned
  # directories are exempt and X bits are cleared. The suid bit must be
  # set on the directory as well; see chmod(1). PC owners can't see/set
  # ownerships so they keep getting their toes trodden on. This saves
  # you all the support calls as the filesystem it's used on will act as
  # they expect: "It's my dir so it must be my file".
  #
  options         SUIDDIR
  
  # NFS options:
  options         NFS_MINATTRTIMO=3       # VREG attrib cache timeout in sec
  options         NFS_MAXATTRTIMO=60
  options         NFS_MINDIRATTRTIMO=30   # VDIR attrib cache timeout in sec
  options         NFS_MAXDIRATTRTIMO=60
  options         NFS_DEBUG               # Enable NFS Debugging
  
  #
  # Add support for the EXT2FS filesystem of Linux fame.  Be a bit
  # careful with this - the ext2fs code has a tendency to lag behind
  # changes and not be exercised very much, so mounting read/write could
  # be dangerous (and even mounting read only could result in panics.)
  #
  options         EXT2FS
  
  # The system memory devices; /dev/mem, /dev/kmem
  device          mem
  
  # The kernel symbol table device; /dev/ksyms
  device          ksyms
  
  # Optional character code conversion support with LIBICONV.
  # Each option requires their base file system and LIBICONV.
  options         CD9660_ICONV
  options         MSDOSFS_ICONV
  options         UDF_ICONV
  
  
  #####################################################################
  # POSIX P1003.1B
  
  # Real time extensions added in the 1993 POSIX
  # _KPOSIX_PRIORITY_SCHEDULING: Build in _POSIX_PRIORITY_SCHEDULING
  
  options         _KPOSIX_PRIORITY_SCHEDULING
  # p1003_1b_semaphores are very experimental,
  # user should be ready to assist in debugging if problems arise.
  options         P1003_1B_SEMAPHORES
  
  # POSIX message queue
  options         P1003_1B_MQUEUE
  
  #####################################################################
  # SECURITY POLICY PARAMETERS
  
  # Support for BSM audit
  options         AUDIT
  
  # Support for Mandatory Access Control (MAC):
  options         MAC
  options         MAC_BIBA
  options         MAC_BSDEXTENDED
  options         MAC_DDB
  options         MAC_IFOFF
  options         MAC_LOMAC
  options         MAC_MLS
  options         MAC_NONE
  options         MAC_NTPD
  options         MAC_PARTITION
  options         MAC_PORTACL
  options         MAC_PRIORITY
  options         MAC_SEEOTHERUIDS
  options         MAC_STUB
  options         MAC_TEST
  options         MAC_VERIEXEC
  options         MAC_VERIEXEC_SHA1
  options         MAC_VERIEXEC_SHA256
  options         MAC_VERIEXEC_SHA384
  options         MAC_VERIEXEC_SHA512
  device          mac_veriexec_parser
  
  # Support for Capsicum
  options         CAPABILITIES    # fine-grained rights on file descriptors
  options         CAPABILITY_MODE # sandboxes with no global namespace access
  
  
  #####################################################################
  # CLOCK OPTIONS
  
  # The granularity of operation is controlled by the kernel option HZ (default
  # frequency of 1000 Hz or a period 1ms between calls). Virtual machine guests
  # use a value of 100. Lower values may lower overhead at the expense of accuracy
  # of scheduling, though the adaptive tick code reduces that overhead.
  
  options         HZ=100
  
  # Enable support for the kernel PLL to use an external PPS signal,
  # under supervision of [x]ntpd(8)
  # More info in ntpd documentation: http://www.eecis.udel.edu/~ntp
  
  options         PPS_SYNC
  
  # Enable support for generic feed-forward clocks in the kernel.
  # The feed-forward clock support is an alternative to the feedback oriented
  # ntpd/system clock approach, and is to be used with a feed-forward
  # synchronization algorithm such as the RADclock:
  # More info here: http://www.synclab.org/radclock
  
  options         FFCLOCK
  
  
  #####################################################################
  # SCSI DEVICES
  
  # SCSI DEVICE CONFIGURATION
  
  # The SCSI subsystem consists of the `base' SCSI code, a number of
  # high-level SCSI device `type' drivers, and the low-level host-adapter
  # device drivers.  The host adapters are listed in the ISA and PCI
  # device configuration sections below.
  #
  # It is possible to wire down your SCSI devices so that a given bus,
  # target, and LUN always come on line as the same device unit.  In
  # earlier versions the unit numbers were assigned in the order that
  # the devices were probed on the SCSI bus.  This means that if you
  # removed a disk drive, you may have had to rewrite your /etc/fstab
  # file, and also that you had to be careful when adding a new disk
  # as it may have been probed earlier and moved your device configuration
  # around.
  
  # This old behavior is maintained as the default behavior.  The unit
  # assignment begins with the first non-wired down unit for a device
  # type.  For example, if you wire a disk as "da3" then the first
  # non-wired disk will be assigned da4.
  
  # The syntax for wiring down devices is:
  
  envvar          hint.scbus.0.at="ahc0"
  envvar          hint.scbus.1.at="ahc1"
  envvar          hint.scbus.1.bus="0"
  envvar          hint.scbus.3.at="ahc2"
  envvar          hint.scbus.3.bus="0"
  envvar          hint.scbus.2.at="ahc2"
  envvar          hint.scbus.2.bus="1"
  envvar          hint.da.0.at="scbus0"
  envvar          hint.da.0.target="0"
  envvar          hint.da.0.unit="0"
  envvar          hint.da.1.at="scbus3"
  envvar          hint.da.1.target="1"
  envvar          hint.da.2.at="scbus2"
  envvar          hint.da.2.target="3"
  envvar          hint.sa.1.at="scbus1"
  envvar          hint.sa.1.target="6"
  
  # "units" (SCSI logical unit number) that are not specified are
  # treated as if specified as LUN 0.
  
  # All SCSI devices allocate as many units as are required.
  
  # The ch driver drives SCSI Media Changer ("jukebox") devices.
  #
  # The da driver drives SCSI Direct Access ("disk") and Optical Media
  # ("WORM") devices.
  #
  # The sa driver drives SCSI Sequential Access ("tape") devices.
  #
  # The cd driver drives SCSI Read Only Direct Access ("cd") devices.
  #
  # The ses driver drives SCSI Environment Services ("ses") and
  # SAF-TE ("SCSI Accessible Fault-Tolerant Enclosure") devices.
  #
  # The pt driver drives SCSI Processor devices.
  #
  # The sg driver provides a passthrough API that is compatible with the
  # Linux SG driver.  It will work in conjunction with the Linuxulator
  # to run linux SG apps.  It can also stand on its own and provide
  # source level API compatibility for porting apps to FreeBSD.
  #
  # Target Mode support is provided here but also requires that a SIM
  # (SCSI Host Adapter Driver) provide support as well.
  #
  # The targ driver provides target mode support as a Processor type device.
  # It exists to give the minimal context necessary to respond to Inquiry
  # commands. There is a sample user application that shows how the rest
  # of the command support might be done in /usr/share/examples/scsi_target.
  #
  # The targbh driver provides target mode support and exists to respond
  # to incoming commands that do not otherwise have a logical unit assigned
  # to them.
  #
  # The pass driver provides a passthrough API to access the CAM subsystem.
  
  device          scbus           #base SCSI code
  device          ch              #SCSI media changers
  device          da              #SCSI direct access devices (aka disks)
  device          sa              #SCSI tapes
  device          cd              #SCSI CD-ROMs
  device          ses             #Enclosure Services (SES and SAF-TE)
  device          pt              #SCSI processor
  device          targ            #SCSI Target Mode Code
  device          targbh          #SCSI Target Mode Blackhole Device
  device          pass            #CAM passthrough driver
  device          sg              #Linux SCSI passthrough
  device          ctl             #CAM Target Layer
  
  # CAM OPTIONS:
  # debugging options:
  # CAMDEBUG              Compile in all possible debugging.
  # CAM_DEBUG_COMPILE     Debug levels to compile in.
  # CAM_DEBUG_FLAGS       Debug levels to enable on boot.
  # CAM_DEBUG_BUS         Limit debugging to the given bus.
  # CAM_DEBUG_TARGET      Limit debugging to the given target.
  # CAM_DEBUG_LUN         Limit debugging to the given lun.
  # CAM_DEBUG_DELAY       Delay in us after printing each debug line.
  # CAM_IO_STATS          Publish additional CAM device statics by sysctl
  #
  # CAM_MAX_HIGHPOWER: Maximum number of concurrent high power (start unit) cmds
  # SCSI_NO_SENSE_STRINGS: When defined disables sense descriptions
  # SCSI_NO_OP_STRINGS: When defined disables opcode descriptions
  # SCSI_DELAY: The number of MILLISECONDS to freeze the SIM (scsi adapter)
  #             queue after a bus reset, and the number of milliseconds to
  #             freeze the device queue after a bus device reset.  This
  #             can be changed at boot and runtime with the
  #             kern.cam.scsi_delay tunable/sysctl.
  options         CAMDEBUG
  options         CAM_DEBUG_COMPILE=-1
  options         CAM_DEBUG_FLAGS=(CAM_DEBUG_INFO|CAM_DEBUG_PROBE|CAM_DEBUG_PERIPH)
  options         CAM_DEBUG_BUS=-1
  options         CAM_DEBUG_TARGET=-1
  options         CAM_DEBUG_LUN=-1
  options         CAM_DEBUG_DELAY=1
  options         CAM_MAX_HIGHPOWER=4
  options         SCSI_NO_SENSE_STRINGS
  options         SCSI_NO_OP_STRINGS
  options         SCSI_DELAY=5000 # Be pessimistic about Joe SCSI device
  options         CAM_IOSCHED_DYNAMIC
  options         CAM_IO_STATS
  options         CAM_TEST_FAILURE
  
  # Options for the CAM CDROM driver:
  # CHANGER_MIN_BUSY_SECONDS: Guaranteed minimum time quantum for a changer LUN
  # CHANGER_MAX_BUSY_SECONDS: Maximum time quantum per changer LUN, only
  #                           enforced if there is I/O waiting for another LUN
  # The compiled in defaults for these variables are 2 and 10 seconds,
  # respectively.
  #
  # These can also be changed on the fly with the following sysctl variables:
  # kern.cam.cd.changer.min_busy_seconds
  # kern.cam.cd.changer.max_busy_seconds
  #
  options         CHANGER_MIN_BUSY_SECONDS=2
  options         CHANGER_MAX_BUSY_SECONDS=10
  
  # Options for the CAM sequential access driver:
  # SA_IO_TIMEOUT: Timeout for read/write/wfm  operations, in minutes
  # SA_SPACE_TIMEOUT: Timeout for space operations, in minutes
  # SA_REWIND_TIMEOUT: Timeout for rewind operations, in minutes
  # SA_ERASE_TIMEOUT: Timeout for erase operations, in minutes
  # SA_1FM_AT_EOD: Default to model which only has a default one filemark at EOT.
  options         SA_IO_TIMEOUT=4
  options         SA_SPACE_TIMEOUT=60
  options         SA_REWIND_TIMEOUT=(2*60)
  options         SA_ERASE_TIMEOUT=(4*60)
  options         SA_1FM_AT_EOD
  
  # Optional timeout for the CAM processor target (pt) device
  # This is specified in seconds.  The default is 60 seconds.
  options         SCSI_PT_DEFAULT_TIMEOUT=60
  
  # Optional enable of doing SES passthrough on other devices (e.g., disks)
  #
  # Normally disabled because a lot of newer SCSI disks report themselves
  # as having SES capabilities, but this can then clot up attempts to build
  # a topology with the SES device that's on the box these drives are in....
  options         SES_ENABLE_PASSTHROUGH
  
  
  #####################################################################
  # MISCELLANEOUS DEVICES AND OPTIONS
  
  device          pty             #BSD-style compatibility pseudo ttys
  device          nmdm            #back-to-back tty devices
  device          md              #Memory/malloc disk
  device          snp             #Snoop device - to look at pty/vty/etc..
  device          ccd             #Concatenated disk driver
  device          firmware        #firmware(9) support
  
  # Kernel side iconv library
  options         LIBICONV
  
  # Size of the kernel message buffer.  Should be N * pagesize.
  options         MSGBUF_SIZE=40960
  
  
  #####################################################################
  # HARDWARE BUS CONFIGURATION
  
  #
  # PCI bus & PCI options:
  #
  device          pci
  options         PCI_HP                  # PCI-Express native HotPlug
  options         PCI_IOV                 # PCI SR-IOV support
  
  
  #####################################################################
  # HARDWARE DEVICE CONFIGURATION
  
  # For ISA the required hints are listed.
  # PCI, CardBus, and SD/MMC are self identifying buses, so
  # no hints are needed.
  
  #
  # Mandatory devices:
  #
  
  # These options are valid for other keyboard drivers as well.
  options         KBD_DISABLE_KEYMAP_LOAD # refuse to load a keymap
  options         KBD_INSTALL_CDEV        # install a CDEV entry in /dev
  
  device          kbdmux                  # keyboard multiplexer
  options         KBDMUX_DFLT_KEYMAP      # specify the built-in keymap
  makeoptions     KBDMUX_DFLT_KEYMAP=it.iso
  
  options         FB_DEBUG                # Frame buffer debugging
  
  # Enable experimental features of the syscons terminal emulator (teken).
  options         TEKEN_CONS25            # cons25-style terminal emulation
  options         TEKEN_UTF8              # UTF-8 output handling
  
  # The vt video console driver.
  device          vt
  options         VT_ALT_TO_ESC_HACK=1    # Prepend ESC sequence to ALT keys
  options         VT_MAXWINDOWS=16        # Number of virtual consoles
  options         VT_TWOBUTTON_MOUSE      # Use right mouse button to paste
  
  # The following options set the maximum framebuffer size.
  options         VT_FB_MAX_HEIGHT=480
  options         VT_FB_MAX_WIDTH=640
  
  # The following options will let you change the default vt terminal colors.
  options         TERMINAL_NORM_ATTR=(FG_GREEN|BG_BLACK)
  options         TERMINAL_KERN_ATTR=(FG_LIGHTRED|BG_BLACK)
  
  #
  # Optional devices:
  #
  
  #
  # SCSI host adapters:
  #
  # aacraid: Adaptec by PMC RAID controllers, Series 6/7/8 and upcoming
  #          families. Container interface, CAM required.
  # ahc: Adaptec 274x/284x/2910/293x/294x/394x/3950x/3960x/398X/4944/
  #      19160x/29160x, aic7770/aic78xx
  # ahd: Adaptec 29320/39320 Controllers.
  # isp: Qlogic ISP 1020, 1040 and 1040B PCI SCSI host adapters,
  #      ISP 1240 Dual Ultra SCSI, ISP 1080 and 1280 (Dual) Ultra2,
  #      ISP 12160 Ultra3 SCSI,
  #      Qlogic ISP 2100 and ISP 2200 1Gb Fibre Channel host adapters.
  #      Qlogic ISP 2300 and ISP 2312 2Gb Fibre Channel host adapters.
  #      Qlogic ISP 2322 and ISP 6322 2Gb Fibre Channel host adapters.
  # ispfw: Firmware module for Qlogic host adapters
  # mpr: LSI-Logic MPT/Fusion Gen 3
  # mps: LSI-Logic MPT/Fusion Gen 2
  # mpt: LSI-Logic MPT/Fusion 53c1020 or 53c1030 Ultra4
  #      or FC9x9 Fibre Channel host adapters.
  # sym: Symbios/Logic 53C8XX family of PCI-SCSI I/O processors:
  #      53C810, 53C810A, 53C815, 53C825,  53C825A, 53C860, 53C875,
  #      53C876, 53C885,  53C895, 53C895A, 53C896,  53C897, 53C1510D,
  #      53C1010-33, 53C1010-66.
  
  device          aacraid
  device          ahc
  device          ahd
  device          isp
  envvar          hint.isp.0.disable="1"
  envvar          hint.isp.0.role="3"
  envvar          hint.isp.0.prefer_iomap="1"
  envvar          hint.isp.0.prefer_memmap="1"
  envvar          hint.isp.0.fwload_disable="1"
  envvar          hint.isp.0.ignore_nvram="1"
  envvar          hint.isp.0.fullduplex="1"
  envvar          hint.isp.0.topology="lport"
  envvar          hint.isp.0.topology="nport"
  envvar          hint.isp.0.topology="lport-only"
  envvar          hint.isp.0.topology="nport-only"
  # we can't get u_int64_t types, nor can we get strings if it's got
  # a leading 0x, hence this silly dodge.
  envvar          hint.isp.0.portwnn="w50000000aaaa0000"
  envvar          hint.isp.0.nodewnn="w50000000aaaa0001"
  device          ispfw
  device          mpr                     # LSI-Logic MPT-Fusion 3
  device          mps                     # LSI-Logic MPT-Fusion 2
  device          mpt                     # LSI-Logic MPT-Fusion
  device          sym
  
  # The aic7xxx driver will attempt to use memory mapped I/O for all PCI
  # controllers that have it configured only if this option is set. Unfortunately,
  # this doesn't work on some motherboards, which prevents it from being the
  # default.
  options         AHC_ALLOW_MEMIO
  
  # Dump the contents of the ahc controller configuration PROM.
  options         AHC_DUMP_EEPROM
  
  # Bitmap of units to enable targetmode operations.
  options         AHC_TMODE_ENABLE
  
  # Compile in Aic7xxx Debugging code.
  options         AHC_DEBUG
  
  # Aic7xxx driver debugging options. See sys/dev/aic7xxx/aic7xxx.h
  options         AHC_DEBUG_OPTS
  
  # Print register bitfields in debug output.  Adds ~128k to driver
  # See ahc(4).
  options         AHC_REG_PRETTY_PRINT
  
  # Compile in aic79xx debugging code.
  options         AHD_DEBUG
  
  # Aic79xx driver debugging options.  Adds ~215k to driver.  See ahd(4).
  options         AHD_DEBUG_OPTS=0xFFFFFFFF
  
  # Print human-readable register definitions when debugging
  options         AHD_REG_PRETTY_PRINT
  
  # Bitmap of units to enable targetmode operations.
  options         AHD_TMODE_ENABLE
  
  # Options used in dev/iscsi (Software iSCSI stack)
  #
  options         ISCSI_INITIATOR_DEBUG=9
  
  # Options used in dev/isp/ (Qlogic SCSI/FC driver).
  #
  #       ISP_TARGET_MODE         -       enable target mode operation
  #
  options         ISP_TARGET_MODE=1
  #
  #       ISP_DEFAULT_ROLES       -       default role
  #               none=0
  #               target=1
  #               initiator=2
  #               both=3                  (not supported currently)
  #
  #       ISP_INTERNAL_TARGET             (trivial internal disk target, for testing)
  #
  options         ISP_DEFAULT_ROLES=0
  
  #options        SYM_SETUP_SCSI_DIFF     #-HVD support for 825a, 875, 885
                                          # disabled:0 (default), enabled:1
  #options        SYM_SETUP_PCI_PARITY    #-PCI parity checking
                                          # disabled:0, enabled:1 (default)
  #options        SYM_SETUP_MAX_LUN       #-Number of LUNs supported
                                          # default:8, range:[1..64]
  
  #
  # Compaq "CISS" RAID controllers (SmartRAID 5* series)
  # These controllers have a SCSI-like interface, and require the
  # CAM infrastructure.
  #
  device          ciss
  
  #
  # Compaq Smart RAID, Mylex DAC960 and AMI MegaRAID controllers.  Only
  # one entry is needed; the code will find and configure all supported
  # controllers.
  #
  device          ida             # Compaq Smart RAID
  device          mlx             # Mylex DAC960
  device          mfi             # LSI MegaRAID SAS
  device          mfip            # LSI MegaRAID SAS passthrough, requires CAM
  options         MFI_DEBUG
  device          mrsas           # LSI/Avago MegaRAID SAS/SATA, 6Gb/s and 12Gb/s
  
  #
  # 3ware ATA RAID
  #
  device          twe             # 3ware ATA RAID
  
  #
  # Serial ATA host controllers:
  #
  # ahci: Advanced Host Controller Interface (AHCI) compatible
  # mvs:  Marvell 88SX50XX/88SX60XX/88SX70XX/SoC controllers
  # siis: SiliconImage SiI3124/SiI3132/SiI3531 controllers
  #
  # These drivers are part of cam(4) subsystem. They supersede less featured
  # ata(4) subsystem drivers, supporting same hardware.
  
  device          ahci
  device          mvs
  device          siis
  
  #
  # The 'ATA' driver supports all legacy ATA/ATAPI controllers, including
  # PC Card devices. You only need one "device ata" for it to find all
  # PCI and PC Card ATA/ATAPI devices on modern machines.
  # Alternatively, individual bus and chipset drivers may be chosen by using
  # the 'atacore' driver then selecting the drivers on a per vendor basis.
  # For example to build a system which only supports a VIA chipset,
  # omit 'ata' and include the 'atacore', 'atapci' and 'atavia' drivers.
  device          ata
  
  # Modular ATA
  #device         atacore         # Core ATA functionality
  #device         ataisa          # ISA bus support
  #device         atapci          # PCI bus support; only generic chipset support
  
  # PCI ATA chipsets
  #device         ataacard        # ACARD
  #device         ataacerlabs     # Acer Labs Inc. (ALI)
  #device         ataamd          # American Micro Devices (AMD)
  #device         ataati          # ATI
  #device         atacenatek      # Cenatek
  #device         atacypress      # Cypress
  #device         atacyrix        # Cyrix
  #device         atahighpoint    # HighPoint
  #device         ataintel        # Intel
  #device         ataite          # Integrated Technology Inc. (ITE)
  #device         atajmicron      # JMicron
  #device         atamarvell      # Marvell
  #device         atamicron       # Micron
  #device         atanational     # National
  #device         atanetcell      # NetCell
  #device         atanvidia       # nVidia
  #device         atapromise      # Promise
  #device         ataserverworks  # ServerWorks
  #device         atasiliconimage # Silicon Image Inc. (SiI) (formerly CMD)
  #device         atasis          # Silicon Integrated Systems Corp.(SiS)
  #device         atavia          # VIA Technologies Inc.
  
  #
  # For older non-PCI, non-PnPBIOS systems, these are the hints lines to add:
  envvar          hint.ata.0.at="isa"
  envvar          hint.ata.0.port="0x1f0"
  envvar          hint.ata.0.irq="14"
  envvar          hint.ata.1.at="isa"
  envvar          hint.ata.1.port="0x170"
  envvar          hint.ata.1.irq="15"
  
  #
  # uart: generic driver for serial interfaces.
  #
  device          uart
  
  # Options for uart(4)
  options         UART_PPS_ON_CTS         # Do time pulse capturing using CTS
                                          # instead of DCD.
  options         UART_POLL_FREQ          # Set polling rate, used when hw has
                                          # no interrupt support (50 Hz default).
  
  # The following hint should only be used for pure ISA devices.  It is not
  # needed otherwise.  Use of hints is strongly discouraged.
  envvar          hint.uart.0.at="isa"
  
  # The following 3 hints are used when the UART is a system device (i.e., a
  # console or debug port), but only on platforms that don't have any other
  # means to pass the information to the kernel.  The unit number of the hint
  # is only used to bundle the hints together.  There is no relation to the
  # unit number of the probed UART.
  envvar          hint.uart.0.port="0x3f8"
  envvar          hint.uart.0.flags="0x10"
  envvar          hint.uart.0.baud="115200"
  
  # `flags' for serial drivers that support consoles, like uart(4):
  #       0x10    enable console support for this unit.  Other console flags
  #               (if applicable) are ignored unless this is set.  Enabling
  #               console support does not make the unit the preferred console.
  #               Boot with -h or set boot_serial=YES in the loader.
  #               Currently, at most one unit can have console support; the
  #               first one (in config file order) with this flag set is
  #               preferred.
  #       0x80    use this port for serial line gdb support in ddb.  Also known
  #               as debug port.
  #
  
  # Options for serial drivers that support consoles:
  options         BREAK_TO_DEBUGGER       # A BREAK/DBG on the console goes to
                                          # ddb, if available.
  
  # Solaris implements a new BREAK which is initiated by a character
  # sequence CR ~ ^b which is similar to a familiar pattern used on
  # Sun servers by the Remote Console.  There are FreeBSD extensions:
  # CR ~ ^p requests force panic and CR ~ ^r requests a clean reboot.
  options         ALT_BREAK_TO_DEBUGGER
  
  # Serial Communications Controller
  # Supports the Freescale/NXP QUad Integrated and Zilog Z8530 multi-channel
  # communications controllers.
  device          scc
  
  # PCI Universal Communications driver
  # Supports various multi port PCI I/O cards.
  device          puc
  
  #
  # Network interfaces:
  #
  # MII bus support is required for many PCI Ethernet NICs,
  # namely those which use MII-compliant transceivers or implement
  # transceiver control interfaces that operate like an MII.  Adding
  # "device miibus" to the kernel config pulls in support for the generic
  # miibus API, the common support for bit-bang'ing the MII and all
  # of the PHY drivers, including a generic one for PHYs that aren't
  # specifically handled by an individual driver.  Support for specific
  # PHYs may be built by adding "device mii", "device mii_bitbang" if
  # needed by the NIC driver and then adding the appropriate PHY driver.
  device          mii             # Minimal MII support
  device          mii_bitbang     # Common module for bit-bang'ing the MII
  device          miibus          # MII support w/ bit-bang'ing and all PHYs
  
  device          acphy           # Altima Communications AC101
  device          amphy           # AMD AM79c873 / Davicom DM910{1,2}
  device          atphy           # Attansic/Atheros F1
  device          axphy           # Asix Semiconductor AX88x9x
  device          bmtphy          # Broadcom BCM5201/BCM5202 and 3Com 3c905C
  device          bnxt            # Broadcom NetXtreme-C/NetXtreme-E
  device          brgphy          # Broadcom BCM54xx/57xx 1000baseTX
  device          cgem            # Cadence GEM Gigabit Ethernet
  device          ciphy           # Cicada/Vitesse CS/VSC8xxx
  device          e1000phy        # Marvell 88E1000 1000/100/10-BT
  device          gentbi          # Generic 10-bit 1000BASE-{LX,SX} fiber ifaces
  device          icsphy          # ICS ICS1889-1893
  device          ip1000phy       # IC Plus IP1000A/IP1001
  device          jmphy           # JMicron JMP211/JMP202
  device          lxtphy          # Level One LXT-970
  device          nsgphy          # NatSemi DP8361/DP83865/DP83891
  device          nsphy           # NatSemi DP83840A
  device          nsphyter        # NatSemi DP83843/DP83815
  device          pnaphy          # HomePNA
  device          qsphy           # Quality Semiconductor QS6612
  device          rdcphy          # RDC Semiconductor R6040
  device          rgephy          # RealTek 8169S/8110S/8211B/8211C
  device          rlphy           # RealTek 8139
  device          rlswitch        # RealTek 8305
  device          smcphy          # SMSC LAN91C111
  device          tdkphy          # TDK 89Q2120
  device          truephy         # LSI TruePHY
  device          xmphy           # XaQti XMAC II
  
  # ae:   Support for gigabit ethernet adapters based on the Attansic/Atheros
  #       L2 PCI-Express FastEthernet controllers.
  # age:  Support for gigabit ethernet adapters based on the Attansic/Atheros
  #       L1 PCI express gigabit ethernet controllers.
  # alc:  Support for Atheros AR8131/AR8132 PCIe ethernet controllers.
  # ale:  Support for Atheros AR8121/AR8113/AR8114 PCIe ethernet controllers.
  # ath:  Atheros a/b/g WiFi adapters (requires ath_hal and wlan)
  # bce:  Broadcom NetXtreme II (BCM5706/BCM5708) PCI/PCIe Gigabit Ethernet
  #       adapters.
  # bfe:  Broadcom BCM4401 Ethernet adapter.
  # bge:  Support for gigabit ethernet adapters based on the Broadcom
  #       BCM570x family of controllers, including the 3Com 3c996-T,
  #       the Netgear GA302T, the SysKonnect SK-9D21 and SK-9D41, and
  #       the embedded gigE NICs on Dell PowerEdge 2550 servers.
  # bnxt: Broadcom NetXtreme-C and NetXtreme-E PCIe 10/25/50G Ethernet adapters.
  # bxe:  Broadcom NetXtreme II (BCM5771X/BCM578XX) PCIe 10Gb Ethernet
  #       adapters.
  # bwi:  Broadcom BCM430* and BCM431* family of wireless adapters.
  # bwn:  Broadcom BCM43xx family of wireless adapters.
  # cas:  Sun Cassini/Cassini+ and National Semiconductor DP83065 Saturn
  # cxgb: Chelsio T3 based 1GbE/10GbE PCIe Ethernet adapters.
  # cxgbe:Chelsio T4, T5, and T6-based 1/10/25/40/100GbE PCIe Ethernet
  #       adapters.
  # cxgbev: Chelsio T4, T5, and T6-based PCIe Virtual Functions.
  # dc:   Support for PCI fast ethernet adapters based on the DEC/Intel 21143
  #       and various workalikes including:
  #       the ADMtek AL981 Comet and AN985 Centaur, the ASIX Electronics
  #       AX88140A and AX88141, the Davicom DM9100 and DM9102, the Lite-On
  #       82c168 and 82c169 PNIC, the Lite-On/Macronix LC82C115 PNIC II
  #       and the Macronix 98713/98713A/98715/98715A/98725 PMAC. This driver
  #       replaces the old al, ax, dm, pn and mx drivers.  List of brands:
  #       Digital DE500-BA, Kingston KNE100TX, D-Link DFE-570TX, SOHOware SFA110,
  #       SVEC PN102-TX, CNet Pro110B, 120A, and 120B, Compex RL100-TX,
  #       LinkSys LNE100TX, LNE100TX V2.0, Jaton XpressNet, Alfa Inc GFC2204,
  #       KNE110TX.
  # em:   Intel Pro/1000 Gigabit Ethernet 82542, 82543, 82544 based adapters.
  # fxp:  Intel EtherExpress Pro/100B
  #       (hint of prefer_iomap can be done to prefer I/O instead of Mem mapping)
  # gem:  Apple GMAC/Sun ERI/Sun GEM
  # jme:  JMicron JMC260 Fast Ethernet/JMC250 Gigabit Ethernet based adapters.
  # le:   AMD Am7900 LANCE and Am79C9xx PCnet
  # lge:  Support for PCI gigabit ethernet adapters based on the Level 1
  #       LXT1001 NetCellerator chipset. This includes the D-Link DGE-500SX,
  #       SMC TigerCard 1000 (SMC9462SX), and some Addtron cards.
  # lio:  Support for Cavium 23XX Ethernet adapters
  # malo: Marvell Libertas wireless NICs.
  # mwl:  Marvell 88W8363 802.11n wireless NICs.
  #       Requires the mwl firmware module
  # mwlfw: Marvell 88W8363 firmware
  # msk:  Support for gigabit ethernet adapters based on the Marvell/SysKonnect
  #       Yukon II Gigabit controllers, including 88E8021, 88E8022, 88E8061,
  #       88E8062, 88E8035, 88E8036, 88E8038, 88E8050, 88E8052, 88E8053,
  #       88E8055, 88E8056 and D-Link 560T/550SX.
  # mlxfw: Mellanox firmware update module.
  # mlx5: Mellanox ConnectX-4 and ConnectX-4 LX IB and Eth shared code module.
  # mlx5en:Mellanox ConnectX-4 and ConnectX-4 LX PCIe Ethernet adapters.
  # my:   Myson Fast Ethernet (MTD80X, MTD89X)
  # nge:  Support for PCI gigabit ethernet adapters based on the National
  #       Semiconductor DP83820 and DP83821 chipset. This includes the
  #       SMC EZ Card 1000 (SMC9462TX), D-Link DGE-500T, Asante FriendlyNet
  #       GigaNIX 1000TA and 1000TPC, the Addtron AEG320T, the Surecom
  #       EP-320G-TX and the Netgear GA622T.
  # oce:  Emulex 10 Gbit adapters (OneConnect Ethernet)
  # ral:  Ralink Technology IEEE 802.11 wireless adapter
  # re:   RealTek 8139C+/8169/816xS/811xS/8101E PCI/PCIe Ethernet adapter
  # rl:   Support for PCI fast ethernet adapters based on the RealTek 8129/8139
  #       chipset.  Note that the RealTek driver defaults to using programmed
  #       I/O to do register accesses because memory mapped mode seems to cause
  #       severe lockups on SMP hardware.  This driver also supports the
  #       Accton EN1207D `Cheetah' adapter, which uses a chip called
  #       the MPX 5030/5038, which is either a RealTek in disguise or a
  #       RealTek workalike.  Note that the D-Link DFE-530TX+ uses the RealTek
  #       chipset and is supported by this driver, not the 'vr' driver.
  # rtwn: RealTek wireless adapters.
  # rtwnfw: RealTek wireless firmware.
  # sge:  Silicon Integrated Systems SiS190/191 Fast/Gigabit Ethernet adapter
  # sis:  Support for NICs based on the Silicon Integrated Systems SiS 900,
  #       SiS 7016 and NS DP83815 PCI fast ethernet controller chips.
  # sk:   Support for the SysKonnect SK-984x series PCI gigabit ethernet NICs.
  #       This includes the SK-9841 and SK-9842 single port cards (single mode
  #       and multimode fiber) and the SK-9843 and SK-9844 dual port cards
  #       (also single mode and multimode).
  #       The driver will autodetect the number of ports on the card and
  #       attach each one as a separate network interface.
  # ste:  Sundance Technologies ST201 PCI fast ethernet controller, includes
  #       the D-Link DFE-550TX.
  # stge: Support for gigabit ethernet adapters based on the Sundance/Tamarack
  #       TC9021 family of controllers, including the Sundance ST2021/ST2023,
  #       the Sundance/Tamarack TC9021, the D-Link DL-4000 and ASUS NX1101.
  # ti:   Support for PCI gigabit ethernet NICs based on the Alteon Networks
  #       Tigon 1 and Tigon 2 chipsets.  This includes the Alteon AceNIC, the
  #       3Com 3c985, the Netgear GA620 and various others.  Note that you will
  #       probably want to bump up kern.ipc.nmbclusters a lot to use this driver.
  # vr:   Support for various fast ethernet adapters based on the VIA
  #       Technologies VT3043 `Rhine I' and VT86C100A `Rhine II' chips,
  #       including the D-Link DFE520TX and D-Link DFE530TX (see 'rl' for
  #       DFE530TX+), the Hawking Technologies PN102TX, and the AOpen/Acer ALN-320.
  # vte:  DM&P Vortex86 RDC R6040 Fast Ethernet
  # xl:   Support for the 3Com 3c900, 3c905, 3c905B and 3c905C (Fast)
  #       Etherlink XL cards and integrated controllers.  This includes the
  #       integrated 3c905B-TX chips in certain Dell Optiplex and Dell
  #       Precision desktop machines and the integrated 3c905-TX chips
  #       in Dell Latitude laptop docking stations.
  #       Also supported: 3Com 3c980(C)-TX, 3Com 3cSOHO100-TX, 3Com 3c450-TX
  
  # PCI Ethernet NICs that use the common MII bus controller code.
  device          ae              # Attansic/Atheros L2 FastEthernet
  device          age             # Attansic/Atheros L1 Gigabit Ethernet
  device          alc             # Atheros AR8131/AR8132 Ethernet
  device          ale             # Atheros AR8121/AR8113/AR8114 Ethernet
  device          bce             # Broadcom BCM5706/BCM5708 Gigabit Ethernet
  device          bfe             # Broadcom BCM440x 10/100 Ethernet
  device          bge             # Broadcom BCM570xx Gigabit Ethernet
  device          cas             # Sun Cassini/Cassini+ and NS DP83065 Saturn
  device          dc              # DEC/Intel 21143 and various workalikes
  device          et              # Agere ET1310 10/100/Gigabit Ethernet
  device          fxp             # Intel EtherExpress PRO/100B (82557, 82558)
  envvar          hint.fxp.0.prefer_iomap="0"
  device          gem             # Apple GMAC/Sun ERI/Sun GEM
  device          jme             # JMicron JMC250 Gigabit/JMC260 Fast Ethernet
  device          lge             # Level 1 LXT1001 gigabit Ethernet
  device          lio             # Support for Cavium 23XX Ethernet adapters
  device          mlxfw           # Mellanox firmware update module
  device          mlx5            # Shared code module between IB and Ethernet
  device          mlx5en          # Mellanox ConnectX-4 and ConnectX-4 LX
  device          msk             # Marvell/SysKonnect Yukon II Gigabit Ethernet
  device          my              # Myson Fast Ethernet (MTD80X, MTD89X)
  device          nge             # NatSemi DP83820 gigabit Ethernet
  device          re              # RealTek 8139C+/8169/8169S/8110S
  device          rl              # RealTek 8129/8139
  device          sge             # Silicon Integrated Systems SiS190/191
  device          sis             # Silicon Integrated Systems SiS 900/SiS 7016
  device          sk              # SysKonnect SK-984x & SK-982x gigabit Ethernet
  device          ste             # Sundance ST201 (D-Link DFE-550TX)
  device          stge            # Sundance/Tamarack TC9021 gigabit Ethernet
  device          vr              # VIA Rhine, Rhine II
  device          vte             # DM&P Vortex86 RDC R6040 Fast Ethernet
  device          xl              # 3Com 3c90x (``Boomerang'', ``Cyclone'')
  
  # PCI/PCI-X/PCIe Ethernet NICs that use iflib infrastructure
  device          iflib
  device          em              # Intel Pro/1000 Gigabit Ethernet
  device          ix              # Intel Pro/10Gbe PCIE Ethernet
  device          ixv             # Intel Pro/10Gbe PCIE Ethernet VF
  
  # PCI Ethernet NICs.
  device          cxgb            # Chelsio T3 10 Gigabit Ethernet
  device          cxgb_t3fw       # Chelsio T3 10 Gigabit Ethernet firmware
  device          cxgbe           # Chelsio T4-T6 1/10/25/40/100 Gigabit Ethernet
  device          cxgbev          # Chelsio T4-T6 Virtual Functions
  device          le              # AMD Am7900 LANCE and Am79C9xx PCnet
  device          mxge            # Myricom Myri-10G 10GbE NIC
  device          oce             # Emulex 10 GbE (OneConnect Ethernet)
  device          ti              # Alteon Networks Tigon I/II gigabit Ethernet
  
  # PCI IEEE 802.11 Wireless NICs
  device          ath             # Atheros pci/cardbus NIC's
  device          ath_hal         # pci/cardbus chip support
  #device         ath_ar5210      # AR5210 chips
  #device         ath_ar5211      # AR5211 chips
  #device         ath_ar5212      # AR5212 chips
  #device         ath_rf2413
  #device         ath_rf2417
  #device         ath_rf2425
  #device         ath_rf5111
  #device         ath_rf5112
  #device         ath_rf5413
  #device         ath_ar5416      # AR5416 chips
  # All of the AR5212 parts have a problem when paired with the AR71xx
  # CPUS.  These parts have a bug that triggers a fatal bus error on the AR71xx
  # only.  Details of the exact nature of the bug are sketchy, but some can be
  # found at https://forum.openwrt.org/viewtopic.php?pid=70060 on pages 4, 5 and
  # 6.  This option enables this workaround.  There is a performance penalty
  # for this work around, but without it things don't work at all.  The DMA
  # from the card usually bursts 128 bytes, but on the affected CPUs, only
  # 4 are safe.
  options         AH_RXCFG_SDMAMW_4BYTES
  #device         ath_ar9160      # AR9160 chips
  #device         ath_ar9280      # AR9280 chips
  #device         ath_ar9285      # AR9285 chips
  device          ath_rate_sample # SampleRate tx rate control for ath
  device          bwi             # Broadcom BCM430* BCM431*
  device          bwn             # Broadcom BCM43xx
  device          malo            # Marvell Libertas wireless NICs.
  device          mwl             # Marvell 88W8363 802.11n wireless NICs.
  device          mwlfw
  device          ral             # Ralink Technology RT2500 wireless NICs.
  device          rtwn            # Realtek wireless NICs
  device          rtwnfw
  
  # Use sf_buf(9) interface for jumbo buffers on ti(4) controllers.
  #options        TI_SF_BUF_JUMBO
  # Turn on the header splitting option for the ti(4) driver firmware.  This
  # only works for Tigon II chips, and has no effect for Tigon I chips.
  # This option requires the TI_SF_BUF_JUMBO option above.
  #options        TI_JUMBO_HDRSPLIT
  
  # These two options allow manipulating the mbuf cluster size and mbuf size,
  # respectively.  Be very careful with NIC driver modules when changing
  # these from their default values, because that can potentially cause a
  # mismatch between the mbuf size assumed by the kernel and the mbuf size
  # assumed by a module.  The only driver that currently has the ability to
  # detect a mismatch is ti(4).
  options         MCLSHIFT=11     # mbuf cluster shift in bits, 11 == 2KB
  options         MSIZE=256       # mbuf size in bytes
  
  #
  # Sound drivers
  #
  # sound: The generic sound driver.
  #
  
  device          sound
  
  #
  # snd_*: Device-specific drivers.
  #
  # The flags of the device tell the device a bit more info about the
  # device that normally is obtained through the PnP interface.
  #       bit  2..0   secondary DMA channel;
  #       bit  4      set if the board uses two dma channels;
  #       bit 15..8   board type, overrides autodetection; leave it
  #                   zero if don't know what to put in (and you don't,
  #                   since this is unsupported at the moment...).
  #
  # snd_als4000:          Avance Logic ALS4000 PCI.
  # snd_atiixp:           ATI IXP 200/300/400 PCI.
  # snd_cmi:              CMedia CMI8338/CMI8738 PCI.
  # snd_cs4281:           Crystal Semiconductor CS4281 PCI.
  # snd_csa:              Crystal Semiconductor CS461x/428x PCI. (except
  #                       4281)
  # snd_emu10k1:          Creative EMU10K1 PCI and EMU10K2 (Audigy) PCI.
  # snd_emu10kx:          Creative SoundBlaster Live! and Audigy
  # snd_envy24:           VIA Envy24 and compatible, needs snd_spicds.
  # snd_envy24ht:         VIA Envy24HT and compatible, needs snd_spicds.
  # snd_es137x:           Ensoniq AudioPCI ES137x PCI.
  # snd_fm801:            Forte Media FM801 PCI.
  # snd_hda:              Intel High Definition Audio (Controller) and
  #                       compatible.
  # snd_hdspe:            RME HDSPe AIO and RayDAT.
  # snd_ich:              Intel ICH AC'97 and some more audio controllers
  #                       embedded in a chipset, for example nVidia
  #                       nForce controllers.
  # snd_maestro3:         ESS Technology Maestro-3/Allegro PCI.
  # snd_neomagic:         Neomagic 256 AV/ZX PCI.
  # snd_solo:             ESS Solo-1x PCI.
  # snd_spicds:           SPI codec driver, needed by Envy24/Envy24HT drivers.
  # snd_t4dwave:          Trident 4DWave DX/NX PCI, Sis 7018 PCI and Acer Labs
  #                       M5451 PCI.
  # snd_uaudio:           USB audio.
  # snd_via8233:          VIA VT8233x PCI.
  # snd_via82c686:        VIA VT82C686A PCI.
  # snd_vibes:            S3 Sonicvibes PCI.
  
  device          snd_als4000
  device          snd_atiixp
  device          snd_cmi
  device          snd_cs4281
  device          snd_csa
  device          snd_emu10k1
  device          snd_emu10kx
  device          snd_envy24
  device          snd_envy24ht
  device          snd_es137x
  device          snd_fm801
  device          snd_hda
  device          snd_hdspe
  device          snd_ich
  device          snd_maestro3
  device          snd_neomagic
  device          snd_solo
  device          snd_spicds
  device          snd_t4dwave
  device          snd_uaudio
  device          snd_via8233
  device          snd_via82c686
  device          snd_vibes
  
  # For non-PnP sound cards:
  envvar          hint.pcm.0.at="isa"
  envvar          hint.pcm.0.irq="10"
  envvar          hint.pcm.0.drq="1"
  envvar          hint.pcm.0.flags="0x0"
  envvar          hint.sbc.0.at="isa"
  envvar          hint.sbc.0.port="0x220"
  envvar          hint.sbc.0.irq="5"
  envvar          hint.sbc.0.drq="1"
  envvar          hint.sbc.0.flags="0x15"
  envvar          hint.gusc.0.at="isa"
  envvar          hint.gusc.0.port="0x220"
  envvar          hint.gusc.0.irq="5"
  envvar          hint.gusc.0.drq="1"
  envvar          hint.gusc.0.flags="0x13"
  
  #
  # Following options are intended for debugging/testing purposes:
  #
  # SND_DEBUG                    Enable extra debugging code that includes
  #                              sanity checking and possible increase of
  #                              verbosity.
  #
  # SND_DIAGNOSTIC               Similar in a spirit of INVARIANTS/DIAGNOSTIC,
  #                              zero tolerance against inconsistencies.
  #
  # SND_FEEDER_MULTIFORMAT       By default, only 16/32 bit feeders are compiled
  #                              in. This options enable most feeder converters
  #                              except for 8bit. WARNING: May bloat the kernel.
  #
  # SND_FEEDER_FULL_MULTIFORMAT  Ditto, but includes 8bit feeders as well.
  #
  # SND_FEEDER_RATE_HP           (feeder_rate) High precision 64bit arithmetic
  #                              as much as possible (the default trying to
  #                              avoid it). Possible slowdown.
  #
  # SND_PCM_64                   (Only applicable for i386/32bit arch)
  #                              Process 32bit samples through 64bit
  #                              integer/arithmetic. Slight increase of dynamic
  #                              range at a cost of possible slowdown.
  #
  # SND_OLDSTEREO                Only 2 channels are allowed, effectively
  #                              disabling multichannel processing.
  #
  options         SND_DEBUG
  options         SND_DIAGNOSTIC
  options         SND_FEEDER_MULTIFORMAT
  options         SND_FEEDER_FULL_MULTIFORMAT
  options         SND_FEEDER_RATE_HP
  options         SND_PCM_64
  options         SND_OLDSTEREO
  
  #
  # Cardbus
  #
  # cbb: pci/CardBus bridge implementing YENTA interface
  # cardbus: CardBus slots
  device          cbb
  device          cardbus
  
  #
  # MMC/SD
  #
  # mmc           MMC/SD bus
  # mmcsd         MMC/SD memory card
  # sdhci         Generic PCI SD Host Controller
  # rtsx          Realtek SD card reader (RTS5209, RTS5227, ...)
  device          mmc
  device          mmcsd
  device          sdhci
  device          rtsx
  
  #
  # SMB bus
  #
  # System Management Bus support is provided by the 'smbus' device.
  # Access to the SMBus device is via the 'smb' device (/dev/smb*),
  # which is a child of the 'smbus' device.
  #
  # Supported devices:
  # smb           standard I/O through /dev/smb*
  #
  # Supported SMB interfaces:
  # iicsmb        I2C to SMB bridge with any iicbus interface
  # intpm         Intel PIIX4 (82371AB, 82443MX) Power Management Unit
  # alpm          Acer Aladdin-IV/V/Pro2 Power Management Unit
  # ichsmb        Intel ICH SMBus controller chips (82801AA, 82801AB, 82801BA)
  # viapm         VIA VT82C586B/596B/686A and VT8233 Power Management Unit
  # amdpm         AMD 756 Power Management Unit
  # amdsmb        AMD 8111 SMBus 2.0 Controller
  # nfpm          NVIDIA nForce Power Management Unit
  # nfsmb         NVIDIA nForce2/3/4 MCP SMBus 2.0 Controller
  # ismt          Intel SMBus 2.0 controller chips (on Atom S1200, C2000)
  #
  device          smbus           # Bus support, required for smb below.
  
  device          intpm
  device          alpm
  device          ichsmb
  device          viapm
  device          amdpm
  device          amdsmb
  device          nfpm
  device          nfsmb
  device          ismt
  
  device          smb
  
  # SMBus peripheral devices
  #
  # jedec_dimm    Asset and temperature reporting for DDR3 and DDR4 DIMMs
  #
  device          jedec_dimm
  
  # I2C Bus
  #
  # Philips i2c bus support is provided by the `iicbus' device.
  #
  # Supported devices:
  # ic    i2c network interface
  # iic   i2c standard io
  # iicsmb i2c to smb bridge. Allow i2c i/o with smb commands.
  # iicoc simple polling driver for OpenCores I2C controller
  #
  # Other:
  # iicbb generic I2C bit-banging code (needed by lpbb)
  #
  device          iicbus          # Bus support, required for ic/iic/iicsmb below.
  device          iicbb           # bitbang driver; implements i2c on a pair of gpio pins
  
  device          ic
  device          iic             # userland access to i2c slave devices via ioctl(8)
  device          iicsmb          # smb over i2c bridge
  device          iicoc           # OpenCores I2C controller support
  
  # I2C bus multiplexer (mux) devices
  device          iicmux          # i2c mux core driver
  device          iic_gpiomux     # i2c mux hardware controlled via gpio pins
  device          ltc430x         # LTC4305 and LTC4306 i2c mux chips
  
  # I2C peripheral devices
  #
  device          ad7418          # Analog Devices temp and voltage sensor
  device          ads111x         # Texas Instruments ADS101x and ADS111x ADCs
  device          ds1307          # Dallas DS1307 RTC and compatible
  device          ds13rtc         # All Dallas/Maxim ds13xx chips
  device          ds1672          # Dallas DS1672 RTC
  device          ds3231          # Dallas DS3231 RTC + temperature
  device          fan53555        # Fairchild Semi FAN53555/SYR82x Regulator
  device          icee            # AT24Cxxx and compatible EEPROMs
  device          isl12xx         # Intersil ISL12xx RTC
  device          lm75            # LM75 compatible temperature sensor
  device          nxprtc          # NXP RTCs: PCA/PFC212x PCA/PCF85xx
  device          rtc8583         # Epson RTC-8583
  device          s35390a         # Seiko Instruments S-35390A RTC
  device          sy8106a         # Silergy Corp. SY8106A buck regulator
  
  # Parallel-Port Bus
  #
  # Parallel port bus support is provided by the `ppbus' device.
  # Multiple devices may be attached to the parallel port, devices
  # are automatically probed and attached when found.
  #
  # Supported devices:
  # lpt   Parallel Printer
  # plip  Parallel network interface
  # ppi   General-purpose I/O ("Geek Port") + IEEE1284 I/O
  # pps   Pulse per second Timing Interface
  # lpbb  Philips official parallel port I2C bit-banging interface
  # pcfclock Parallel port clock driver.
  #
  # Supported interfaces:
  # ppc   ISA-bus parallel port interfaces.
  #
  
  options         PPC_PROBE_CHIPSET # Enable chipset specific detection
                                    # (see flags in ppc(4))
  options         DEBUG_1284      # IEEE1284 signaling protocol debug
  options         PERIPH_1284     # Makes your computer act as an IEEE1284
                                  # compliant peripheral
  options         DONTPROBE_1284  # Avoid boot detection of PnP parallel devices
  options         LPT_DEBUG       # Printer driver debug
  options         PPC_DEBUG       # Parallel chipset level debug
  options         PLIP_DEBUG      # Parallel network IP interface debug
  options         PCFCLOCK_VERBOSE         # Verbose pcfclock driver
  options         PCFCLOCK_MAX_RETRIES=5   # Maximum read tries (default 10)
  
  device          ppc
  envvar          hint.ppc.0.at="isa"
  envvar          hint.ppc.0.irq="7"
  device          ppbus
  device          lpt
  device          plip
  device          ppi
  device          pps
  device          lpbb
  device          pcfclock
  
  # General Purpose I/O pins
  device          dwgpio          # Synopsys DesignWare APB GPIO Controller
  device          gpio            # gpio interfaces and bus support
  device          gpiobacklight   # sysctl control of gpio-based backlight
  device          gpioiic         # i2c via gpio bitbang
  device          gpiokeys        # kbd(4) glue for gpio-based key input
  device          gpioled         # led(4) gpio glue
  device          gpiopower       # event handler for gpio-based powerdown
  device          gpiopps         # Pulse per second input from gpio pin
  device          gpioregulator   # extres/regulator glue for gpio pin
  device          gpiospi         # SPI via gpio bitbang
  device          gpioths         # 1-wire temp/humidity sensor on gpio pin
  
  # Pulse width modulation
  device          pwmbus          # pwm interface and bus support
  device          pwmc            # userland control access to pwm outputs
  
  #
  # Etherswitch framework and drivers
  #
  # etherswitch   The etherswitch(4) framework
  # miiproxy      Proxy device for miibus(4) functionality
  # 
  # Switch hardware support:
  # arswitch      Atheros switches
  # ip17x         IC+ 17x family switches
  # rtl8366r      Realtek RTL8366 switches
  # ukswitch      Multi-PHY switches
  #
  device          etherswitch
  device          miiproxy
  device          arswitch
  device          ip17x
  device          rtl8366rb
  device          ukswitch
  
  # Kernel BOOTP support
  
  options         BOOTP           # Use BOOTP to obtain IP address/hostname
                                  # Requires NFSCL and NFS_ROOT
  options         BOOTP_NFSROOT   # NFS mount root filesystem using BOOTP info
  options         BOOTP_NFSV3     # Use NFS v3 to NFS mount root
  options         BOOTP_COMPAT    # Workaround for broken bootp daemons.
  options         BOOTP_WIRED_TO=fxp0 # Use interface fxp0 for BOOTP
  options         BOOTP_BLOCKSIZE=8192 # Override NFS block size
  
  #
  # Enable software watchdog routines, even if hardware watchdog is present.
  # By default, software watchdog timer is enabled only if no hardware watchdog
  # is present.
  #
  options         SW_WATCHDOG
  
  #
  # Add the software deadlock resolver thread.
  #
  options         DEADLKRES
  
  #
  # Disable swapping of stack pages.  This option removes all
  # code which actually performs swapping, so it's not possible to turn
  # it back on at run-time.
  #
  # This is sometimes usable for systems which don't have any swap space
  # (see also sysctl "vm.disable_swapspace_pageouts")
  #
  #options        NO_SWAPPING
  
  # Set the number of sf_bufs to allocate. sf_bufs are virtual buffers
  # for sendfile(2) that are used to map file VM pages, and normally
  # default to a quantity that is roughly 16*MAXUSERS+512. You would
  # typically want about 4 of these for each simultaneous file send.
  #
  options         NSFBUFS=1024
  
  #
  # Enable extra debugging code for locks.  This stores the filename and
  # line of whatever acquired the lock in the lock itself, and changes a
  # number of function calls to pass around the relevant data.  This is
  # not at all useful unless you are debugging lock code.  Note that
  # modules should be recompiled as this option modifies KBI.
  #
  options         DEBUG_LOCKS
  
  #####################################################################
  # HID support
  device          hid             # Generic HID support
  options         HID_DEBUG       # enable debug msgs
  device          hidbus          # HID bus
  device          hidmap          # HID to evdev mapping
  device          hidraw          # Raw access driver
  options         HIDRAW_MAKE_UHID_ALIAS  # install /dev/uhid alias
  device          hconf           # Multitouch configuration TLC
  device          hcons           # Consumer controls
  device          hgame           # Generic game controllers
  device          hkbd            # HID keyboard
  device          hms             # HID mouse
  device          hmt             # HID multitouch (MS-compatible)
  device          hpen            # Generic pen driver
  device          hsctrl          # System controls
  device          ps4dshock       # Sony PS4 DualShock 4 gamepad driver
  device          xb360gp         # XBox 360 gamepad driver
  
  #####################################################################
  # USB support
  # UHCI controller
  device          uhci
  # OHCI controller
  device          ohci
  # EHCI controller
  device          ehci
  # XHCI controller
  device          xhci
  # SL811 Controller
  #device         slhci
  # General USB code (mandatory for USB)
  device          usb
  #
  # USB Double Bulk Pipe devices
  device          udbp
  # USB temperature meter
  device          ugold
  # USB LED
  device          uled
  # Human Interface Device (anything with buttons and dials)
  device          uhid
  # USB keyboard
  device          ukbd
  # USB printer
  device          ulpt
  # USB mass storage driver (Requires scbus and da)
  device          umass
  # USB mass storage driver for device-side mode
  device          usfs
  # USB support for Belkin F5U109 and Magic Control Technology serial adapters
  device          umct
  # USB modem support
  device          umodem
  # USB mouse
  device          ums
  # USB touchpad(s)
  device          atp
  device          wsp
  # eGalax USB touch screen
  device          uep
  # Diamond Rio 500 MP3 player
  device          urio
  # HID-over-USB driver
  device          usbhid
  
  #
  # USB serial support
  device          ucom
  # USB support for 3G modem cards by Option, Novatel, Huawei and Sierra
  device          u3g
  # USB support for Technologies ARK3116 based serial adapters
  device          uark
  # USB support for Belkin F5U103 and compatible serial adapters
  device          ubsa
  # USB support for serial adapters based on the FT8U100AX and FT8U232AM
  device          uftdi
  # USB support for some Windows CE based serial communication.
  device          uipaq
  # USB support for Prolific PL-2303 serial adapters
  device          uplcom
  # USB support for Silicon Laboratories CP2101/CP2102 based USB serial adapters
  device          uslcom
  # USB Visor and Palm devices
  device          uvisor
  # USB serial support for DDI pocket's PHS
  device          uvscom
  #
  # USB ethernet support
  device          uether
  # ADMtek USB ethernet. Supports the LinkSys USB100TX,
  # the Billionton USB100, the Melco LU-ATX, the D-Link DSB-650TX
  # and the SMC 2202USB. Also works with the ADMtek AN986 Pegasus
  # eval board.
  device          aue
  
  # ASIX Electronics AX88172 USB 2.0 ethernet driver. Used in the
  # LinkSys USB200M and various other adapters.
  device          axe
  # ASIX Electronics AX88178A/AX88179 USB 2.0/3.0 gigabit ethernet driver.
  device          axge
  
  #
  # Devices which communicate using Ethernet over USB, particularly
  # Communication Device Class (CDC) Ethernet specification. Supports
  # Sharp Zaurus PDAs, some DOCSIS cable modems and so on.
  device          cdce
  #
  # CATC USB-EL1201A USB ethernet. Supports the CATC Netmate
  # and Netmate II, and the Belkin F5U111.
  device          cue
  #
  # Kawasaki LSI ethernet. Supports the LinkSys USB10T,
  # Entrega USB-NET-E45, Peracom Ethernet Adapter, the
  # 3Com 3c19250, the ADS Technologies USB-10BT, the ATen UC10T,
  # the Netgear EA101, the D-Link DSB-650, the SMC 2102USB
  # and 2104USB, and the Corega USB-T.
  device          kue
  #
  # RealTek RTL8150 USB to fast ethernet. Supports the Melco LUA-KTX
  # and the GREEN HOUSE GH-USB100B.
  device          rue
  #
  # Davicom DM9601E USB to fast ethernet. Supports the Corega FEther USB-TXC.
  device          udav
  #
  # RealTek RTL8152/RTL8153 USB Ethernet driver
  device          ure
  #
  # Moschip MCS7730/MCS7840 USB to fast ethernet. Supports the Sitecom LN030.
  device          mos
  #
  # HSxPA devices from Option N.V
  device          uhso
  
  # Realtek RTL8188SU/RTL8191SU/RTL8192SU wireless driver
  device          rsu
  #
  # Ralink Technology RT2501USB/RT2601USB wireless driver
  device          rum
  # Ralink Technology RT2700U/RT2800U/RT3000U wireless driver
  device          run
  #
  # Atheros AR5523 wireless driver
  device          uath
  #
  # Conexant/Intersil PrismGT wireless driver
  device          upgt
  #
  # Ralink Technology RT2500USB wireless driver
  device          ural
  #
  # RNDIS USB ethernet driver
  device          urndis
  # Realtek RTL8187B/L wireless driver
  device          urtw
  #
  # ZyDas ZD1211/ZD1211B wireless driver
  device          zyd
  #
  # Sierra USB wireless driver
  device          usie
  
  # 
  # debugging options for the USB subsystem
  #
  options         USB_DEBUG
  options         U3G_DEBUG
  
  # options for ukbd:
  options         UKBD_DFLT_KEYMAP        # specify the built-in keymap
  makeoptions     UKBD_DFLT_KEYMAP=jp.106
  
  # options for uplcom:
  options         UPLCOM_INTR_INTERVAL=100        # interrupt pipe interval
                                                  # in milliseconds
  
  # options for uvscom:
  options         UVSCOM_DEFAULT_OPKTSIZE=8       # default output packet size
  options         UVSCOM_INTR_INTERVAL=100        # interrupt pipe interval
                                                  # in milliseconds
  
  #####################################################################
  # FireWire support
  
  device          firewire        # FireWire bus code
  device          sbp             # SCSI over Firewire (Requires scbus and da)
  device          sbp_targ        # SBP-2 Target mode  (Requires scbus and targ)
  device          fwe             # Ethernet over FireWire (non-standard!)
  device          fwip            # IP over FireWire (RFC2734 and RFC3146)
  
  #####################################################################
  # dcons support (Dumb Console Device)
  
  device          dcons                   # dumb console driver
  device          dcons_crom              # FireWire attachment
  options         DCONS_BUF_SIZE=16384    # buffer size
  options         DCONS_POLL_HZ=100       # polling rate
  options         DCONS_FORCE_CONSOLE=0   # force to be the primary console
  options         DCONS_FORCE_GDB=1       # force to be the gdb device
  
  #####################################################################
  # crypto subsystem
  #
  # This is a port of the OpenBSD crypto framework.  Include this when
  # configuring IPSEC and when you have a h/w crypto device to accelerate
  # user applications that link to OpenSSL.
  #
  # Drivers are ports from OpenBSD with some simple enhancements that have
  # been fed back to OpenBSD.
  
  device          crypto          # core crypto support
  
  # Only install the cryptodev device if you are running tests, or know
  # specifically why you need it.  In most cases, it is not needed and
  # will make things slower.
  device          cryptodev       # /dev/crypto for access to h/w
  
  device          rndtest         # FIPS 140-2 entropy tester
  
  device          ccr             # Chelsio T6
  
  device          hifn            # Hifn 7951, 7781, etc.
  options         HIFN_DEBUG      # enable debugging support: hw.hifn.debug
  options         HIFN_RNDTEST    # enable rndtest support
  
  #####################################################################
  
  
  #
  # Embedded system options:
  #
  # An embedded system might want to run something other than init.
  options         INIT_PATH=/sbin/init:/rescue/init
  
  # Debug options
  options         BUS_DEBUG       # enable newbus debugging
  options         DEBUG_VFS_LOCKS # enable VFS lock debugging
  options         SOCKBUF_DEBUG   # enable sockbuf last record/mb tail checking
  options         IFMEDIA_DEBUG   # enable debugging in net/if_media.c
  
  #
  # Verbose SYSINIT
  #
  # Make the SYSINIT process performed by mi_startup() verbose.  This is very
  # useful when porting to a new architecture.  If DDB is also enabled, this
  # will print function names instead of addresses.  If defined with a value
  # of zero, the verbose code is compiled-in but disabled by default, and can
  # be enabled with the debug.verbose_sysinit=1 tunable.
  options         VERBOSE_SYSINIT
  
  #####################################################################
  # SYSV IPC KERNEL PARAMETERS
  #
  # Maximum number of System V semaphores that can be used on the system at
  # one time.
  options         SEMMNI=11
  
  # Total number of semaphores system wide
  options         SEMMNS=61
  
  # Total number of undo structures in system
  options         SEMMNU=31
  
  # Maximum number of System V semaphores that can be used by a single process
  # at one time.
  options         SEMMSL=61
  
  # Maximum number of operations that can be outstanding on a single System V
  # semaphore at one time.
  options         SEMOPM=101
  
  # Maximum number of undo operations that can be outstanding on a single
  # System V semaphore at one time.
  options         SEMUME=11
  
  # Maximum number of shared memory pages system wide.
  options         SHMALL=1025
  
  # Maximum size, in bytes, of a single System V shared memory region.
  options         SHMMAX=(SHMMAXPGS*PAGE_SIZE+1)
  options         SHMMAXPGS=1025
  
  # Minimum size, in bytes, of a single System V shared memory region.
  options         SHMMIN=2
  
  # Maximum number of shared memory regions that can be used on the system
  # at one time.
  options         SHMMNI=33
  
  # Maximum number of System V shared memory regions that can be attached to
  # a single process at one time.
  options         SHMSEG=9
  
  # Set the amount of time (in seconds) the system will wait before
  # rebooting automatically when a kernel panic occurs.  If set to (-1),
  # the system will wait indefinitely until a key is pressed on the
  # console.
  options         PANIC_REBOOT_WAIT_TIME=16
  
  # Attempt to bypass the buffer cache and put data directly into the
  # userland buffer for read operation when O_DIRECT flag is set on the
  # file.  Both offset and length of the read operation must be
  # multiples of the physical media sector size.
  #
  options         DIRECTIO
  
  # Specify a lower limit for the number of swap I/O buffers.  They are
  # (among other things) used when bypassing the buffer cache due to
  # DIRECTIO kernel option enabled and O_DIRECT flag set on file.
  #
  options         NSWBUF_MIN=120
  
  #####################################################################
  
  # More undocumented options for linting.
  # Note that documenting these is not considered an affront.
  
  options         CAM_DEBUG_DELAY
  
  options         DEBUG
  
  # Kernel filelock debugging.
  options         LOCKF_DEBUG
  
  # System V compatible message queues
  # Please note that the values provided here are used to test kernel
  # building.  The defaults in the sources provide almost the same numbers.
  # MSGSSZ must be a power of 2 between 8 and 1024.
  options         MSGMNB=2049     # Max number of chars in queue
  options         MSGMNI=41       # Max number of message queue identifiers
  options         MSGSEG=2049     # Max number of message segments
  options         MSGSSZ=16       # Size of a message segment
  options         MSGTQL=41       # Max number of messages in system
  
  options         NBUF=512        # Number of buffer headers
  
  options         SC_DEBUG_LEVEL=5        # Syscons debug level
  options         SC_RENDER_DEBUG # syscons rendering debugging
  
  options         VFS_BIO_DEBUG   # VFS buffer I/O debugging
  
  options         KSTACK_MAX_PAGES=32 # Maximum pages to give the kernel stack
  options         KSTACK_USAGE_PROF
  
  # Adaptec Array Controller driver options
  options         AAC_DEBUG       # Debugging levels:
                                  # 0 - quiet, only emit warnings
                                  # 1 - noisy, emit major function
                                  #     points and things done
                                  # 2 - extremely noisy, emit trace
                                  #     items in loops, etc.
  
  # Resource Accounting
  options         RACCT
  
  # Resource Limits
  options         RCTL
  
  # Yet more undocumented options for linting.
  options         MAXFILES=999
  
  # Random number generator
  # Alternative algorithm.
  #options        RANDOM_FENESTRASX
  # Allow the CSPRNG algorithm to be loaded as a module.
  #options        RANDOM_LOADABLE
  # Select this to allow high-rate but potentially expensive
  # harvesting of Slab-Allocator entropy. In very high-rate
  # situations the value of doing this is dubious at best.
  options         RANDOM_ENABLE_UMA       # slab allocator
  
  # Select this to allow high-rate but potentially expensive
  # harvesting of of the m_next pointer in the mbuf. Note that
  # the m_next pointer is NULL except when receiving > 4K
  # jumbo frames or sustained bursts by way of LRO. Thus in
  # the common case it is stirring zero in to the entropy
  # pool. In cases where it is not NULL it is pointing to one
  # of a small (in the thousands to 10s of thousands) number
  # of 256 byte aligned mbufs. Hence it is, even in the best
  # case, a poor source of entropy. And in the absence of actual
  # runtime analysis of entropy collection may mislead the user in
  # to believe that substantially more entropy is being collected
  # than in fact is - leading to a different class of security
  # risk. In high packet rate situations ethernet entropy
  # collection is also very expensive, possibly leading to as
  # much as a 50% drop in packets received.
  # This option is present to maintain backwards compatibility
  # if desired, however it cannot be recommended for use in any
  # environment.
  options         RANDOM_ENABLE_ETHER     # ether_input
  
  # Module to enable execution of application via emulators like QEMU
  options         IMGACT_BINMISC
  
  # zlib I/O stream support
  # This enables support for compressed core dumps.
  options         GZIO
  
  # zstd support
  # This enables support for Zstd compressed core dumps, GEOM_UZIP images,
  # and is required by zfs if statically linked.
  options         ZSTDIO
  
  # BHND(4) drivers
  options         BHND_LOGLEVEL   # Logging threshold level
  
  # evdev interface 
  device          evdev           # input event device support
  options         EVDEV_SUPPORT   # evdev support in legacy drivers
  options         EVDEV_DEBUG     # enable event debug msgs
  device          uinput          # install /dev/uinput cdev
  options         UINPUT_DEBUG    # enable uinput debug msgs
  
  # Encrypted kernel crash dumps.
  options         EKCD
  
  # Serial Peripheral Interface (SPI) support.
  device          spibus          # Bus support.
  device          at45d           # DataFlash driver
  device          cqspi           # 
  device          mx25l           # SPIFlash driver
  device          n25q            # 
  device          spigen          # Generic access to SPI devices from userland.
  # Enable legacy /dev/spigenN name aliases for /dev/spigenX.Y devices.
  options         SPIGEN_LEGACY_CDEVNAME # legacy device names for spigen
  
  # Compression supports.
  device          zlib            # gzip/zlib compression/decompression library
  device          xz              # xz_embedded LZMA de-compression library
  
  # Kernel support for stats(3).
  options         STATS

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