FreeBSD/Linux Kernel Cross Reference
sys/contrib/device-tree/Bindings/reserved-memory/ramoops.txt

     Ramoops oops/panic logger
     =========================
     
     ramoops provides persistent RAM storage for oops and panics, so they can be
     recovered after a reboot. This is a child-node of "/reserved-memory", and
     is named "ramoops" after the backend, rather than "pstore" which is the
     subsystem.
     
     Parts of this storage may be set aside for other persistent log buffers, such
    as kernel log messages, or for optional ECC error-correction data.  The total
    size of these optional buffers must fit in the reserved region.
    
    Any remaining space will be used for a circular buffer of oops and panic
    records.  These records have a configurable size, with a size of 0 indicating
    that they should be disabled.
    
    At least one of "record-size", "console-size", "ftrace-size", or "pmsg-size"
    must be set non-zero, but are otherwise optional as listed below.
    
    
    Required properties:
    
    - compatible: must be "ramoops"
    
    - reg: region of memory that is preserved between reboots
    
    
    Optional properties:
    
    - ecc-size: enables ECC support and specifies ECC buffer size in bytes
      (defaults to 0: no ECC)
    
    - record-size: maximum size in bytes of each kmsg dump.
      (defaults to 0: disabled)
    
    - console-size: size in bytes of log buffer reserved for kernel messages
      (defaults to 0: disabled)
    
    - ftrace-size: size in bytes of log buffer reserved for function tracing and
      profiling (defaults to 0: disabled)
    
    - pmsg-size: size in bytes of log buffer reserved for userspace messages
      (defaults to 0: disabled)
    
    - mem-type: if present, sets the type of mapping is to be used to map the
      reserved region. mem-type: 0 = write-combined (default), 1 = unbuffered,
      2 = cached.
    
    - unbuffered: deprecated, use mem_type instead. If present, and mem_type is
      not specified, it is equivalent to mem_type = 1 and uses unbuffered mappings
      to map the reserved region (defaults to buffered mappings mem_type = 0). If
      both are specified -- "mem_type" overrides "unbuffered".
    
    - max-reason: if present, sets maximum type of kmsg dump reasons to store
      (defaults to 2: log Oopses and Panics). This can be set to INT_MAX to
      store all kmsg dumps. See include/linux/kmsg_dump.h KMSG_DUMP_* for other
      kmsg dump reason values. Setting this to 0 (KMSG_DUMP_UNDEF), means the
      reason filtering will be controlled by the printk.always_kmsg_dump boot
      param: if unset, it will be KMSG_DUMP_OOPS, otherwise KMSG_DUMP_MAX.
    
    - no-dump-oops: deprecated, use max_reason instead. If present, and
      max_reason is not specified, it is equivalent to max_reason = 1
      (KMSG_DUMP_PANIC).
    
    - flags: if present, pass ramoops behavioral flags (defaults to 0,
      see include/linux/pstore_ram.h RAMOOPS_FLAG_* for flag values).

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