On Fri, Jul 08, 2022 at 08:20:46PM +0200, Geert Uytterhoeven wrote: > Add a helper to retrieve the actual number of bits per pixel for a > plane, taking into account the number of characters and pixels per > block for tiled formats. > > Signed-off-by: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> > Reviewed-by: Javier Martinez Canillas <javierm@xxxxxxxxxx> > --- > v3: > - Add Reviewed-by, > > v2: > - Move up. > --- > drivers/gpu/drm/drm_fourcc.c | 19 +++++++++++++++++++ > include/drm/drm_fourcc.h | 1 + > 2 files changed, 20 insertions(+) > > diff --git a/drivers/gpu/drm/drm_fourcc.c b/drivers/gpu/drm/drm_fourcc.c > index 07741b678798b0f1..cf48ea0b2cb70ba8 100644 > --- a/drivers/gpu/drm/drm_fourcc.c > +++ b/drivers/gpu/drm/drm_fourcc.c > @@ -370,6 +370,25 @@ unsigned int drm_format_info_block_height(const struct drm_format_info *info, > } > EXPORT_SYMBOL(drm_format_info_block_height); > > +/** > + * drm_format_info_bpp - number of bits per pixel > + * @info: pixel format info > + * @plane: plane index > + * > + * Returns: > + * The actual number of bits per pixel, depending on the plane index. > + */ > +unsigned int drm_format_info_bpp(const struct drm_format_info *info, int plane) > +{ > + if (!info || plane < 0 || plane >= info->num_planes) > + return 0; > + > + return info->char_per_block[plane] * 8 / > + (drm_format_info_block_width(info, plane) * > + drm_format_info_block_height(info, plane)); Do we really needs this for blocky formats where this is potentially ill-defined? I think if there's no need then this should also return 0 when block_width/height != 1, it doesn't make much sense to compute bpp when it's not really bits per _pixel_. Minimally this needs to check whether the division actually makes sense or whether there's a reminder, and if there's reminder, then fail. But that feels like a bad hack and I think we should avoid it if it's not absolutely necessary. Otherwise lgtm. -Daniel > +} > +EXPORT_SYMBOL(drm_format_info_bpp); > + > /** > * drm_format_info_min_pitch - computes the minimum required pitch in bytes > * @info: pixel format info > diff --git a/include/drm/drm_fourcc.h b/include/drm/drm_fourcc.h > index 22aa64d07c7905e2..3800a7ad7f0cda7a 100644 > --- a/include/drm/drm_fourcc.h > +++ b/include/drm/drm_fourcc.h > @@ -313,6 +313,7 @@ unsigned int drm_format_info_block_width(const struct drm_format_info *info, > int plane); > unsigned int drm_format_info_block_height(const struct drm_format_info *info, > int plane); > +unsigned int drm_format_info_bpp(const struct drm_format_info *info, int plane); > uint64_t drm_format_info_min_pitch(const struct drm_format_info *info, > int plane, unsigned int buffer_width); > > -- > 2.25.1 > -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch