Re: [PATCH] drm: add drm_format_alpha_bits

[Ayan Halder <ayan.halder@arm.com>]

On Fri, Jan 12, 2018 at 04:28:34PM +0200, Ville Syrj?l? wrote:
> On Fri, Jan 12, 2018 at 02:21:16PM +0000, Ayan Halder wrote:
> > drm_format_info does not describe the number of bits used for the alpha
> > channel. That information is useful in a central place like drm_fourcc.c
> > where it can be queried by the drivers that want to determine if 'alpha
> > blending' is to be enabled or not.
> > 
> > Signed-off-by: Ayan Kumar Halder <ayan.halder@arm.com>
> > Reviewed-by: Liviu Dudau <liviu.dudau@arm.com>
> > ---
> >  drivers/gpu/drm/drm_fourcc.c | 154 ++++++++++++++++++++++++-------------------
> >  include/drm/drm_fourcc.h     |   3 +
> >  2 files changed, 89 insertions(+), 68 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/drm_fourcc.c b/drivers/gpu/drm/drm_fourcc.c
> > index 9c0152d..073001b 100644
> > --- a/drivers/gpu/drm/drm_fourcc.c
> > +++ b/drivers/gpu/drm/drm_fourcc.c
> <snip>
> > @@ -348,3 +348,21 @@ int drm_format_plane_height(int height, uint32_t format, int plane)
> >  	return height / info->vsub;
> >  }
> >  EXPORT_SYMBOL(drm_format_plane_height);
> > +
> > +/**
> > + * drm_format_alpha_bits - get the number of bits per pixel
> > + * representing alpha for format
> > + * @format: pixel format (DRM_FORMAT_*)
> > + *
> > + * Returns:
> > + * The number of bits per pixel representing alpha used by the
> > + * specified pixel format.
> > + */
> > +int drm_format_alpha_bits(uint32_t format)
> > +{
> > +	const struct drm_format_info *info;
> > +
> > +	info = drm_format_info(format);
> > +	return info ? info->alpha : 0;
> > +}
> > +EXPORT_SYMBOL(drm_format_alpha_bits);
> 
> Do you have an actual use for this function somewhere?
Currently, we do not have a usage for this function. We need 'alpha'
field for each entry in 'drm_format_info' so as to determine whether
to enable/disable alpha blending in Mali display processor for the
particular color format. 
> 
> > diff --git a/include/drm/drm_fourcc.h b/include/drm/drm_fourcc.h
> > index 6942e84..5513510 100644
> > --- a/include/drm/drm_fourcc.h
> > +++ b/include/drm/drm_fourcc.h
> > @@ -38,6 +38,7 @@ struct drm_mode_fb_cmd2;
> >   * @cpp: Number of bytes per pixel (per plane)
> >   * @hsub: Horizontal chroma subsampling factor
> >   * @vsub: Vertical chroma subsampling factor
> > + * @alpha: Number of bits per pixel representing alpha
> >   */
> >  struct drm_format_info {
> >  	u32 format;
> > @@ -46,6 +47,7 @@ struct drm_format_info {
> >  	u8 cpp[3];
> >  	u8 hsub;
> >  	u8 vsub;
> > +	u8 alpha;
> >  };
> >  
> >  /**
> > @@ -57,6 +59,7 @@ struct drm_format_name_buf {
> >  };
> >  
> >  const struct drm_format_info *__drm_format_info(u32 format);
> > +int drm_format_alpha_bits(u32 format);
> >  const struct drm_format_info *drm_format_info(u32 format);
> >  const struct drm_format_info *
> >  drm_get_format_info(struct drm_device *dev,
> > -- 
> > 2.7.4
> > 
> > _______________________________________________
> > dri-devel mailing list
> > dri-devel@lists.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/dri-devel
> 
> -- 
> Ville Syrj??l??
> Intel OTC
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> dri-devel@lists.freedesktop.org
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