linux-kernel - Re: [PATCH] drm/udl: Add ARGB8888 as a format

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Message-ID: <CAF6AEGs2zCP1SWPzxz4v2CU--yyEsN0+PS3dKM1nOuGyVkCpLg@mail.gmail.com>
Date: Wed, 6 Mar 2024 06:49:15 -0800
From: Rob Clark <robdclark@...il.com>
To: Thomas Zimmermann <tzimmermann@...e.de>
Cc: Douglas Anderson <dianders@...omium.org>, dri-devel@...ts.freedesktop.org, 
	Rob Clark <robdclark@...omium.org>, Javier Martinez Canillas <javierm@...hat.com>, 
	Daniel Vetter <daniel@...ll.ch>, Dave Airlie <airlied@...hat.com>, David Airlie <airlied@...il.com>, 
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, Maxime Ripard <mripard@...nel.org>, 
	Maíra Canal <mcanal@...lia.com>, Sean Paul <sean@...rly.run>, 
	Ville Syrjälä <ville.syrjala@...ux.intel.com>, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/udl: Add ARGB8888 as a format

On Wed, Mar 6, 2024 at 4:18 AM Thomas Zimmermann <tzimmermann@...e.de> wrote:
>
> Hi,
>
> sorry that I did not see the patch before.
>
> Am 27.02.24 um 23:19 schrieb Douglas Anderson:
> > Even though the UDL driver converts to RGB565 internally (see
> > pixel32_to_be16() in udl_transfer.c), it advertises XRGB8888 for
> > compatibility. Let's add ARGB8888 to that list.
>
> We had a heated discussion about the emulation of color formats. It was
> decided that XRGB8888 is the only format to support; and that's only
> because legacy userspace sometimes expects it. Adding other formats to
> the list should not be done easily.

OTOH it is fixing a kernel change that broke userspace

> >
> > This makes UDL devices work on ChromeOS again after commit
> > c91acda3a380 ("drm/gem: Check for valid formats"). Prior to that
> > commit things were "working" because we'd silently treat the ARGB8888
> > that ChromeOS wanted as XRGB8888.
>
> This problem has been caused by userspace. Why can it not be fixed there?
>
> And udl is just one driver. Any other driver without ARGB8888, such as
> simpledrm or ofdrm, would be affected. Do these work?

Probably any driver where ARGB8888 is equivalent to XRGB8888 (ie.
single primary plane, etc) should advertise both.

BR,
-R

> Best regards
> Thomas
>
> >
> > Fixes: c91acda3a380 ("drm/gem: Check for valid formats")
> > Signed-off-by: Douglas Anderson <dianders@...omium.org>
> > ---
> >
> >   drivers/gpu/drm/udl/udl_modeset.c | 1 +
> >   1 file changed, 1 insertion(+)
> >
> > diff --git a/drivers/gpu/drm/udl/udl_modeset.c b/drivers/gpu/drm/udl/udl_modeset.c
> > index 7702359c90c2..0f8d3678770e 100644
> > --- a/drivers/gpu/drm/udl/udl_modeset.c
> > +++ b/drivers/gpu/drm/udl/udl_modeset.c
> > @@ -253,6 +253,7 @@ static int udl_handle_damage(struct drm_framebuffer *fb,
> >   static const uint32_t udl_primary_plane_formats[] = {
> >       DRM_FORMAT_RGB565,
> >       DRM_FORMAT_XRGB8888,
> > +     DRM_FORMAT_ARGB8888,
> >   };
> >
> >   static const uint64_t udl_primary_plane_fmtmods[] = {
>
> --
> --
> Thomas Zimmermann
> Graphics Driver Developer
> SUSE Software Solutions Germany GmbH
> Frankenstrasse 146, 90461 Nuernberg, Germany
> GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman
> HRB 36809 (AG Nuernberg)
>