Hi Tomi,
Thank you for the patch.
On Wed, Feb 12, 2025 at 04:56:05PM +0200, Tomi Valkeinen wrote:
> 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_XV15's (not yet in upstream) 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.
>
> Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
> ---
> drivers/gpu/drm/drm_fourcc.c | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_fourcc.c b/drivers/gpu/drm/drm_fourcc.c
> index 3a94ca211f9c..1e9afbf6ef99 100644
> --- a/drivers/gpu/drm/drm_fourcc.c
> +++ b/drivers/gpu/drm/drm_fourcc.c
> @@ -457,6 +457,13 @@ unsigned int drm_format_info_bpp(const struct drm_format_info *info, int plane)
> if (!info || plane < 0 || plane >= info->num_planes)
> return 0;
>
> + if (info->char_per_block[plane] * 8 %
> + (drm_format_info_block_width(info, plane) *
> + drm_format_info_block_height(info, plane))) {
Can you cache
drm_format_info_block_width(info, plane) *
drm_format_info_block_height(info, plane)
in a local variable to avoid computing it twice ?
> + pr_warn("unable to return an integer bpp\n");
It would be nice to print the warning in the context of the drm device,
but we don't have the required structure here.
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> + return 0;
> + }
> +
> return info->char_per_block[plane] * 8 /
> (drm_format_info_block_width(info, plane) *
> drm_format_info_block_height(info, plane));
--
Regards,
Laurent Pinchart