Re: [PATCH 1/3] drm: Make sure at least one plane supports the fb format

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Mon, Mar 05, 2018 at 12:59:00PM -0800, Eric Anholt wrote:
> Ville Syrjala <ville.syrjala@linux.intel.com> writes:
> 
> > From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> >
> > To make life easier for drivers, let's have the core check that the
> > requested pixel format is supported by at least one plane when creating
> > a new framebuffer.
> >
> > Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > ---
> >  drivers/gpu/drm/drm_framebuffer.c | 26 ++++++++++++++++++++++++++
> >  1 file changed, 26 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/drm_framebuffer.c b/drivers/gpu/drm/drm_framebuffer.c
> > index c0530a1af5e3..155b21e579c4 100644
> > --- a/drivers/gpu/drm/drm_framebuffer.c
> > +++ b/drivers/gpu/drm/drm_framebuffer.c
> > @@ -152,6 +152,23 @@ static int fb_plane_height(int height,
> >  	return DIV_ROUND_UP(height, format->vsub);
> >  }
> >  
> > +static bool planes_have_format(struct drm_device *dev, u32 format)
> > +{
> > +	struct drm_plane *plane;
> > +
> > +	/* TODO: maybe maintain a device level format list? */
> > +	drm_for_each_plane(plane, dev) {
> > +		int i;
> > +
> > +		for (i = 0; i < plane->format_count; i++) {
> > +			if (plane->format_types[i] == format)
> > +				return true;
> > +		}
> > +	}
> > +
> > +	return false;
> > +}
> > +
> >  static int framebuffer_check(struct drm_device *dev,
> >  			     const struct drm_mode_fb_cmd2 *r)
> >  {
> > @@ -168,6 +185,15 @@ static int framebuffer_check(struct drm_device *dev,
> >  		return -EINVAL;
> >  	}
> >  
> > +	if (!planes_have_format(dev, r->pixel_format)) {
> > +		struct drm_format_name_buf format_name;
> > +
> > +		DRM_DEBUG_KMS("unsupported framebuffer format %s\n",
> > +			      drm_get_format_name(r->pixel_format,
> > +						  &format_name));
> > +		return -EINVAL;
> > +	}
> > +
> 
> Won't this break KMS on things like the radeon driver, which doesn't do
> planes?  Maybe check if any universal planes have been registered and
> only do the check in that case?

Hmm. I thought we add the implicit planes always. Apparently
drm_crtc_init() adds a primary with X/ARGB8888, but no more. So
this would break all other formats, which is probably a bit too
aggressive.

I guess I could just skip the check in case any plane has
plane->format_default set. That should be indicating that the driver
doesn't do planes fully. Oh, why exactly is amggpu setting that flag?
Harry?

> 
> Also, "any_planes_have_format()" might be slightly more descriptive.

Or any_plane_has_format()? Is that more englishy? :)

-- 
Ville Syrjälä
Intel OTC
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