projects / deliverable / linux.git / blame
| Commit | Line | Data |
|---|---|---|
| 2a9d832c LL |
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. | |
| 567cf94d SW |
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) |