Documentation/devicetree/bindings/chosen.txt

   1 The chosen node
   2 ---------------
   3
   4 The chosen node does not represent a real device, but serves as a place
   5 for passing data between firmware and the operating system, like boot
   6 arguments. Data in the chosen node does not represent the hardware.
   7
   8
   9 stdout-path property
  10 --------------------
  11
  12 Device trees may specify the device to be used for boot console output
  13 with a stdout-path property under /chosen, as described in ePAPR, e.g.
  14
  15 / {
  16         chosen {
  17                 stdout-path = "/serial@f00:115200";
  18         };
  19
  20         serial@f00 {
  21                 compatible = "vendor,some-uart";
  22                 reg = <0xf00 0x10>;
  23         };
  24 };
  25
  26 If the character ":" is present in the value, this terminates the path.
  27 The meaning of any characters following the ":" is device-specific, and
  28 must be specified in the relevant binding documentation.
  29
  30 For UART devices, the preferred binding is a string in the form:
  31
  32         <baud>{<parity>{<bits>{<flow>}}}
  33
  34 where
  35
  36         baud    - baud rate in decimal
  37         parity  - 'n' (none), 'o', (odd) or 'e' (even)
  38         bits    - number of data bits
  39         flow    - 'r' (rts)
  40
  41 For example: 115200n8r
  42
  43 Implementation note: Linux will look for the property "linux,stdout-path" or
  44 on PowerPC "stdout" if "stdout-path" is not found.  However, the
  45 "linux,stdout-path" and "stdout" properties are deprecated. New platforms
  46 should only use the "stdout-path" property.
  47
  48 linux,booted-from-kexec
  49 -----------------------
  50
  51 This property is set (currently only on PowerPC, and only needed on
  52 book3e) by some versions of kexec-tools to tell the new kernel that it
  53 is being booted by kexec, as the booting environment may differ (e.g.
  54 a different secondary CPU release mechanism)