Re: [RFC 1/9] dt-bindings: display: renesas,cmm: Add R-Car CMM documentation

[Geert Uytterhoeven <geert@linux-m68k.org>]

Hi Laurent,

On Tue, May 28, 2019 at 4:31 PM Laurent Pinchart
<laurent.pinchart@ideasonboard.com> wrote:
> On Tue, May 28, 2019 at 02:37:25PM +0200, Jacopo Mondi wrote:
> > On Sat, May 11, 2019 at 09:16:18PM +0300, Laurent Pinchart wrote:
> > > On Wed, May 08, 2019 at 07:34:20PM +0200, Jacopo Mondi wrote:
> > >> Add device tree bindings documentation for the Renesas R-Car Display
> > >> Unit Color Management Module.
> > >>
> > >> CMM is the image enhancement module available on each R-Car DU video
> > >> channel.
> > >
> > > Not on all of them, V3M and V3H don't include a CMM module.
> > >
> > >> Signed-off-by: Jacopo Mondi <jacopo+renesas@jmondi.org>

> > >> --- /dev/null
> > >> +++ b/Documentation/devicetree/bindings/display/renesas,cmm.txt
> > >> @@ -0,0 +1,24 @@
> > >> +* Renesas R-Car Color Management Unit (CMM)
> > >
> > > It's called Color Management Module in the documentation (hence the CMM
> > > abbreviation)
> > >
> > >> +
> > >> +Renesas R-Car image enhancement module connected to R-Car DU video channels.
> > >> +
> > >> +Required properties:
> > >> + - compatible: shall be:
> > >> +   - "renesas,cmm"
> > >
> > > There's a CMM in R-Car Gen2 with a different feature set, so I think you
> > > need at least two compatible strings. As far as I can tell SoC-specific
> > > compatible strings are required.
> >
> > I assume you meant "SoC-specific compatible strings are NOT required" ?
>
> Correct, sorry.
>
> > Could you otherwise specify why do you think we need a per-SoC
> > compatible, since there are no platform specific data (for now, at
> > least, but considering the CMM seems identical in all SoCs I hardly
> > think we will have any in the near future).
> >
> > Ack on the gen2/gen3 specific strings though.

Usually we do define SoC-specific compatible values in the DT bindings,
unless there is a version register, like on the VPSs.

Why would we want to deviate from that practice for the CMM?

Thanks!

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds