[PATCH 5/5] drm/vmwgfx: Sort primary plane formats by order of preference

[Zack Rusin]

On Wed, Apr 3, 2024 at 3:43 AM Pekka Paalanen
<pekka.paalanen at collabora.com> wrote:
>
> On Tue,  2 Apr 2024 19:28:13 -0400
> Zack Rusin <zack.rusin at broadcom.com> wrote:
>
> > The table of primary plane formats wasn't sorted at all, leading to
> > applications picking our least desirable formats by defaults.
> >
> > Sort the primary plane formats according to our order of preference.
>
> This is good.
>
> > Fixes IGT's kms_atomic plane-invalid-params which assumes that the
> > preferred format is a 32bpp format.
>
> That sounds strange, why would IGT depend on preferred format being
> 32bpp?
>
> That must be an oversight. IGT cannot dictate the format that hardware
> must prefer. XRGB8888 is strongly suggested to be supported in general,
> but why also preferred?

I think it's just a side-effect of the pixman's assert that's failing:
https://cgit.freedesktop.org/drm/igt-gpu-tools/tree/lib/igt_fb.c#n4190
i.e. pixman assumes everything is 4 byte aligned.
I should have rephrased the message as "IGT assumes that the preferred
fb format is 4 byte aligned because our 16bpp formats are packed and
pixman can't convert them".

z