On Thu, Nov 27, 2014 at 12:15:43PM +0000, Mark Rutland wrote:
> 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.
Device-specific is a bit broad though?
> So how about Documentation/devicetree/bindings/serial/stdout-path.txt,
> with something like the following:
There is, however, nothing serial-specific about this functionality -
it console-specific.
Could it be bindings/console/stdout-path.txt?
> ---->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).
For the current situation, which _is_ serial-specific, could we then
add a serial/stdout-path.txt describing the mapping to
uart_parse_options - making that interface an implicit requirement for
the use of stdout-path?
/
Leif
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