[PATCH] drm: Don't create the IN_FORMATS blob when the driver does not provide .format_mod_supported()

[Ville Syrjälä]

On Fri, Oct 23, 2020 at 10:03:50PM +0000, Simon Ser wrote:
> On Friday, October 23, 2020 10:39 PM, Ville Syrjala <ville.syrjala at linux.intel.com> wrote:
> 
> > From: Ville Syrjälä ville.syrjala at linux.intel.com
> >
> > The code responsible for creating the IN_FORMATS
> > blob is broken when the driver doesn't provide a
> > .format_mod_supported() hook. It just copies in
> > the format list, but leaves all the modifier information
> > zeroed. That would indicate (in a very silly way) that
> > there are in fact no supported format+modifier combinations.
> > That is utter nonsense.
> 
> Should we WARN_ON when the driver enables allow_fb_modifiers but
> doesn't populate format_mod_supported?

.format_mod_supported() was supposed to be optional IIRC.

But now that I look at it, it looks like only these
drivers are lacking .format_mod_supported(): exynos, mxsfb,
tiny/cirrus, tiny/gm12u320.

There is some other oddity going on with sun4i which sometimes
uses modifiers sometimes it doesn't. No idea what is going on there.
But it does have .format_mod_supported() at least.

So I guess if we can get exynos, mxsfb, and tiny/* to implement
the hook then we could make it mandatory.

-- 
Ville Syrjälä
Intel