[PATCH v3] drm/plane: Add documentation about software color conversion.

[Maxime Ripard]

Hi,

On Fri, Sep 08, 2023 at 11:21:51AM +0200, Thomas Zimmermann wrote:
> Am 25.08.23 um 16:04 schrieb Jocelyn Falempe:
> [...]
> > + *
> > + *     But there are two exceptions only for dumb buffers:
> > + *     * To support XRGB8888 if it's not supported by the hardware.
> 
> 
> > + *     * Any driver is free to modify its internal representation of the format,
> > + *       as long as it doesn't alter the visible content in any way, and doesn't
> > + *       modify the user-provided buffer. An example would be to drop the
> > + *       padding component from a format to save some memory bandwidth.
> 
> I have strong objections to this point, _especially_ as you're apparently
> trying to sneak this in after our discussion.

I think it's an unfair characterization. This was discussed on
#dri-devel, and went through several rounds over the mailing lists, with
you in Cc for each. How is that sneaking something in?

> NAK on this part from my side.
> 
> If you want userspace to be able to use a certain format, then export the
> corresponding 4cc code. Then let userspace decide what to do about it. If
> userspace pick a certain format, go with it.
> 
> Hence, no implicit conversion from XRGB888 to RGB888, just because it's
> possible.

I'm not sure what's your argument is, really. Last time we discussed
this, you were saying that you were enforcing that rule because that was
the outcome of that (painful) discussion with Pekka and Javier. It turns
out that both Pekka and Javier are ok with the patch, so it's not clear
to me what your objections are at this point.

Are you really arguing that we shouldn't allow a driver to consume less
resources while not affecting any other component in the system in any
way?

Maxime
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