On Wed, Nov 26, 2014 at 09:48:47PM +0000, Andrew Lunn wrote:
> On Wed, Nov 26, 2014 at 09:07:33PM +0000, Grant Likely wrote:
> > On Wed, Nov 26, 2014 at 6:30 PM, Andrew Lunn <andrew@xxxxxxx> wrote:
> > > On Wed, Nov 26, 2014 at 05:40:40PM +0000, Leif Lindholm wrote:
> > >> Support specifying console options (like with console=ttyXN,<options>)
> > >> by appending them to the stdout-path property after a separating ':'.
> > >>
> > >> Example:
> > >> stdout-path = "uart0:115200";
> > >
> > > Hi Leif
> > >
> > > This should be documented somewhere under
> > > Documentation/devicetree/bindings/
> > >
> > > Not sure where thought. Maybe a top level chosen.txt?
> >
> > Actually, this one doesn't. It is already documented in ePAPR
>
> Hi Grant
>
> Humm, do i have an old version of ePAPR?
>
> All i see is that in Table 3-4 It says:
>
> stdout-path O <string> A string that specifies the full path to the
> node representing the device to be used for
> boot console output. If the character ":" is
> present in the value it terminates the
> path. The value may be an alias.
>
> If the stdin-path property is not specified,
> stdout-path should be assumed to define the input device.
>
> So what is before the : is defined. What comes afterwards,
> baudrate/parity/bits/flow control does not appear to the defined in
> ePAPR. Should we not document the extension being added here?
I believe that we should, and it should be relatively trivial to add a
document stating that the format and meaning of the parts after the ':'
are device-specific.
So how about Documentation/devicetree/bindings/serial/stdout-path.txt,
with something like the following:
---->8----
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 cahracters following the ":" is device-specific, and
must be specified in the relevant binding documentation.
---->8----
The more difficult part is documenting those (and I'm still uneasy about
conflating the Linux driver command line options with the DT binding for
that reason).
Thanks,
Mark.
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