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drm/fourcc: Add warning for bad bpp

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drm_format_info_bpp() cannot be used for formats which do not have an
integer bits-per-pixel in a pixel block.

E.g. DRM_FORMAT_P030's plane 0 has three 10-bit pixels (Y components),
and two padding bits, in a 4 byte block. That is 10.666... bits per
pixel when considering the whole 4 byte block, which is what
drm_format_info_bpp() does. Thus a driver that supports such formats
cannot use drm_format_info_bpp(),

It is a driver bug if this happens, but so handle wrong calls by
printing a warning and returning 0.

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Acked-by: Simon Ser <contact@emersion.fr>
Link: https://patch.msgid.link/20260423-xilinx-formats-v10-1-c690c2b8ea89@ideasonboard.com
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
This commit is contained in:
Tomi Valkeinen 2026-04-23 17:21:12 +03:00
parent 457fa9132c
commit 7e68881239
1 changed files with 11 additions and 3 deletions
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14
drivers/gpu/drm/drm_fourcc.c
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@ -491,12 +491,20 @@ EXPORT_SYMBOL(drm_format_info_block_height);
*/
unsigned int drm_format_info_bpp(const struct drm_format_info *info, int plane)
{
unsigned int block_size;
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));
block_size = drm_format_info_block_width(info, plane) *
drm_format_info_block_height(info, plane);
if (info->char_per_block[plane] * 8 % block_size) {
pr_warn("unable to return an integer bpp\n");
return 0;
}
return info->char_per_block[plane] * 8 / block_size;
}
EXPORT_SYMBOL(drm_format_info_bpp);