[PATCH 1/3] drm: Tune up error message during format->bpp/cpp conversion

[Ville Syrjälä]

On Thu, May 12, 2016 at 04:43:05PM +0300, Imre Deak wrote:
> On Thu, 2016-05-12 at 16:10 +0300, Ville Syrjälä wrote:
> > On Thu, May 12, 2016 at 04:00:38PM +0300, Imre Deak wrote:
> > > Returning a 0 bpp/cpp value from these functions isn't ever valid.
> > > In
> > > many cases it can also lead to a div-by-zero possibly at some later
> > > point in time, so make sure we catch such errors as soon as
> > > possible via
> > > louder error reporting.
> > > 
> > > CC: Dave Airlie <airlied at redhat.com>
> > > Signed-off-by: Imre Deak <imre.deak at intel.com>
> > > ---
> > >  drivers/gpu/drm/drm_crtc.c | 10 +++++++---
> > >  1 file changed, 7 insertions(+), 3 deletions(-)
> > > 
> > > diff --git a/drivers/gpu/drm/drm_crtc.c
> > > b/drivers/gpu/drm/drm_crtc.c
> > > index 70f9c68..3a32606 100644
> > > --- a/drivers/gpu/drm/drm_crtc.c
> > > +++ b/drivers/gpu/drm/drm_crtc.c
> > > @@ -5610,8 +5610,8 @@ void drm_fb_get_bpp_depth(uint32_t format,
> > > unsigned int *depth,
> > >  		*bpp = 32;
> > >  		break;
> > >  	default:
> > > -		DRM_DEBUG_KMS("unsupported pixel format %s\n",
> > > -			      drm_get_format_name(format));
> > > +		WARN(1, "unsupported pixel format %s\n",
> > > +		     drm_get_format_name(format));
> > 
> > NAK. This will happen every time drm_helper_mode_fill_fb_struct()
> > is called with a non-RGB format.
> 
> Yep, missed that. So how about handling here those formats explicitly,
> and emitting a warning only for truly unsupported formats?

More work to keep this list updated, and it wouldn't prevent any
div-by-zero with those formats. So I don't really see a point in that.

> 
> > >  		*depth = 0;
> > >  		*bpp = 0;
> > >  		break;
> > > @@ -5666,8 +5666,12 @@ int drm_format_plane_cpp(uint32_t format,
> > > int plane)
> > >  	unsigned int depth;
> > >  	int bpp;
> > >  
> > > -	if (plane >= drm_format_num_planes(format))
> > > +	if (plane >= drm_format_num_planes(format)) {
> > > +		WARN(1, "invalid plane %d for format %s\n",
> > > +		     plane, drm_get_format_name(format));
> > > +
> > 
> > We have this check in many places. Should either convert all or none.
> 
> Ok, I can also change drm_format_plane_width()
> and drm_format_plane_height(). Couldn't spot any other places.

I thought we might have more. I guess not.

> 
> > >  		return 0;
> > > +	}
> > >  
> > >  	switch (format) {
> > >  	case DRM_FORMAT_YUYV:
> > > -- 
> > > 2.5.0
> > > 
> > > _______________________________________________
> > > dri-devel mailing list
> > > dri-devel at lists.freedesktop.org
> > > https://lists.freedesktop.org/mailman/listinfo/dri-devel
> > 

-- 
Ville Syrjälä
Intel OTC