| 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) |