Messages in this thread | | | Date | Tue, 02 Dec 2014 18:24:21 -0800 | From | Frank Rowand <> | Subject | Re: [PATCH v3 1/3] devicetree: of: Add bindings for chosen node, stdout-path |
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On 11/27/2014 9:56 AM, Leif Lindholm wrote: > 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> > --- > Documentation/devicetree/bindings/chosen.txt | 42 ++++++++++++++++++++++++++ > 1 file changed, 42 insertions(+) > create mode 100644 Documentation/devicetree/bindings/chosen.txt > > diff --git a/Documentation/devicetree/bindings/chosen.txt b/Documentation/devicetree/bindings/chosen.txt > new file mode 100644 > index 0000000..9cd74e9 > --- /dev/null > +++ b/Documentation/devicetree/bindings/chosen.txt > @@ -0,0 +1,42 @@ > +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
The code in patch 3/3 adds the extra options feature to the properties:
stdout-path linux,stdout-path stdout [if (IS_ENABLED(CONFIG_PPC) ... ]
> +-------------------- > + > +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 format supported by uart_parse_options() is the > +expected one. In this case, the format of the string is: > + > + <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 >
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