FreeBSD/Linux Kernel Cross Reference
sys/contrib/device-tree/Bindings/chosen.txt

     The chosen node
     ---------------
     
     The chosen node does not represent a real device, but serves as a place
     for passing data between firmware and the operating system, like boot
     arguments. Data in the chosen node does not represent the hardware.
     
     The following properties are recognized:
     
    
    kaslr-seed
    -----------
    
    This property is used when booting with CONFIG_RANDOMIZE_BASE as the
    entropy used to randomize the kernel image base address location. Since
    it is used directly, this value is intended only for KASLR, and should
    not be used for other purposes (as it may leak information about KASLR
    offsets). It is parsed as a u64 value, e.g.
    
    / {
            chosen {
                    kaslr-seed = <0xfeedbeef 0xc0def00d>;
            };
    };
    
    Note that if this property is set from UEFI (or a bootloader in EFI
    mode) when EFI_RNG_PROTOCOL is supported, it will be overwritten by
    the Linux EFI stub (which will populate the property itself, using
    EFI_RNG_PROTOCOL).
    
    stdout-path
    -----------
    
    Device trees may specify the device to be used for boot console output
    with a stdout-path property under /chosen, as described in the Devicetree
    Specification, e.g.
    
    / {
            chosen {
                    stdout-path = "/serial@f00:115200";
            };
    
            serial@f00 {
                    compatible = "vendor,some-uart";
                    reg = <0xf00 0x10>;
            };
    };
    
    If the character ":" is present in the value, this terminates the path.
    The meaning of any characters following the ":" is device-specific, and
    must be specified in the relevant binding documentation.
    
    For UART devices, the preferred binding is a string in the form:
    
            <baud>{<parity>{<bits>{<flow>}}}
    
    where
    
            baud    - baud rate in decimal
            parity  - 'n' (none), 'o', (odd) or 'e' (even)
            bits    - number of data bits
            flow    - 'r' (rts)
    
    For example: 115200n8r
    
    Implementation note: Linux will look for the property "linux,stdout-path" or
    on PowerPC "stdout" if "stdout-path" is not found.  However, the
    "linux,stdout-path" and "stdout" properties are deprecated. New platforms
    should only use the "stdout-path" property.
    
    linux,booted-from-kexec
    -----------------------
    
    This property is set (currently only on PowerPC, and only needed on
    book3e) by some versions of kexec-tools to tell the new kernel that it
    is being booted by kexec, as the booting environment may differ (e.g.
    a different secondary CPU release mechanism)
    
    linux,usable-memory-range
    -------------------------
    
    This property holds a base address and size, describing a limited region in
    which memory may be considered available for use by the kernel. Memory outside
    of this range is not available for use.
    
    This property describes a limitation: memory within this range is only
    valid when also described through another mechanism that the kernel
    would otherwise use to determine available memory (e.g. memory nodes
    or the EFI memory map). Valid memory may be sparse within the range.
    e.g.
    
    / {
            chosen {
                    linux,usable-memory-range = <0x9 0xf0000000 0x0 0x10000000>;
            };
    };
    
    The main usage is for crash dump kernel to identify its own usable
    memory and exclude, at its boot time, any other memory areas that are
   part of the panicked kernel's memory.
   
   While this property does not represent a real hardware, the address
   and the size are expressed in #address-cells and #size-cells,
   respectively, of the root node.
   
   linux,elfcorehdr
   ----------------
   
   This property holds the memory range, the address and the size, of the elf
   core header which mainly describes the panicked kernel's memory layout as
   PT_LOAD segments of elf format.
   e.g.
   
   / {
           chosen {
                   linux,elfcorehdr = <0x9 0xfffff000 0x0 0x800>;
           };
   };
   
   While this property does not represent a real hardware, the address
   and the size are expressed in #address-cells and #size-cells,
   respectively, of the root node.
   
   linux,initrd-start and linux,initrd-end
   ---------------------------------------
   
   These properties hold the physical start and end address of an initrd that's
   loaded by the bootloader. Note that linux,initrd-start is inclusive, but
   linux,initrd-end is exclusive.
   e.g.
   
   / {
           chosen {
                   linux,initrd-start = <0x82000000>;
                   linux,initrd-end = <0x82800000>;
           };
   };

Cache object: 9f44b59e4585e999ce8f8640e1fd2918