Hi,
On Fri, Jan 12, 2018 at 03:43:49PM +0000, Ayan Halder wrote:
> 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@xxxxxxx>
> > > Reviewed-by: Liviu Dudau <liviu.dudau@xxxxxxx>
> > > ---
> > > 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.
Do you need only the info that a particular channel has an alpha
component, or do you also need the number of bits?
In the former case, then my serie sent earlier this week would help I
guess.
Maxime
--
Maxime Ripard, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com
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