[RFC PATCH 0/7] add at91sam9 LCDC DRM driver

[Daniel Vetter]

On Wed, Aug 15, 2018 at 4:45 PM, Rob Herring <robh at kernel.org> wrote:
> On Tue, Aug 14, 2018 at 10:48 PM Sam Ravnborg <sam at ravnborg.org> wrote:
>>
>
> [...]
>
>> > > One DT related Q:
>> > > The LCD Controller supports BGR565, but as this is less common some HW implmentations
>> > > exchange R and B, expessed in the old binding as wiring-mode like this:
>> > >
>> > >     atmel,lcd-wiring-mode: lcd wiring mode "RGB" or "BRG"
>> > >
>> > > How can we express this wiring-mode in a generic way, both in DT and in code?
>> > > Is it something that in DRM belongs to the panel, the encoder, the connector, or?
>> > > And can any of the exisitng flags be used?
>> >
>> > I thought we had come up with a common definition, but I guess it didn't
>> > make it upstream. It's definitely needed and I've been rejecting
>> > anything new that's vendor specific.
>> I found this: https://patchwork.ozlabs.org/patch/659570/
>> The suggestion with a boolean seems simple and I will try that.
>
> That's really too simple to be common. There's been a few other
> attempts[1][2][3] (for Atmel HLCDC in fact) with [3] probably being
> the closest to merging. The binding looked fine to me, but looks like
> the DRM implementation had some issues.
>
> Rob
>
> [1] https://lists.freedesktop.org/archives/dri-devel/2018-April/173089.html
> [2] https://patchwork.kernel.org/patch/9965079/
> [3] http://lists.infradead.org/pipermail/linux-arm-kernel/2018-March/568731.html

There's a standardized bus_format for drm_panel. IIrc there's been
discussions to add something similar to drm_bridge, but didn't go all
that far for reasons.

Lots of drivers just handle this internally in some way. So no idea
why this all got stalled.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch