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    SubjectRe: [PATCH v3 1/3] devicetree: of: Add bindings for chosen node, stdout-path
    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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