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author | Leif Lindholm <leif.lindholm@linaro.org> | 2014-11-27 17:56:05 +0000 |
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committer | Grant Likely <grant.likely@linaro.org> | 2014-12-03 23:12:35 +0000 |
commit | 2a9d832cc9aae21ea827520fef635b6c49a06c6d (patch) | |
tree | 6d2e3b625fc1910b1e09c3ce276859ab39177f23 /Documentation | |
parent | 63ebecc03d2f18411da51a0981bd63818bbd0b54 (diff) | |
download | linux-2a9d832cc9aae21ea827520fef635b6c49a06c6d.tar.bz2 |
of: Add bindings for chosen node, stdout-path
Add a global binding for the chosen node. Include a description of the
stdout-path, and an explicit statement on its extra options in the
context of a UART console.
Opening description stolen from www.devicetree.org, and part of the
remaining text provided by Mark Rutland.
Signed-off-by: Leif Lindholm <leif.lindholm@linaro.org>
[grant.likely: remove reference to uart_parse_options]
Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Grant Likely <grant.likely@linaro.org>
Diffstat (limited to 'Documentation')
-rw-r--r-- | Documentation/devicetree/bindings/chosen.txt | 46 |
1 files changed, 46 insertions, 0 deletions
diff --git a/Documentation/devicetree/bindings/chosen.txt b/Documentation/devicetree/bindings/chosen.txt new file mode 100644 index 000000000000..ed838f453f7a --- /dev/null +++ b/Documentation/devicetree/bindings/chosen.txt @@ -0,0 +1,46 @@ +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. + + +stdout-path property +-------------------- + +Device trees may specify the device to be used for boot console output +with a stdout-path property under /chosen, as described in ePAPR, 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. |