Re: [PATCH v2] drm/format-helper: Make conversion_buf_size() support sub-byte pixel fmts

["Maíra Canal" <mcanal@igalia.com>]

On 3/7/23 18:50, Javier Martinez Canillas wrote:
> There are DRM fourcc formats that have pixels smaller than a byte, but the
> conversion_buf_size() function assumes that pixels are a multiple of bytes
> and use the struct drm_format_info .cpp field to calculate the dst_pitch.
> 
> Instead, calculate it by using the bits per pixel (bpp) and divide it by 8
> to account for formats that have sub-byte pixels.
> 
> Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>

Reviewed-by: Maíra Canal <mcanal@igalia.com>

Best Regards,
- Maíra Canal

> ---
> Tested by making sure that the following command still succeeds:
> 
> ./tools/testing/kunit/kunit.py run \
> --kunitconfig=drivers/gpu/drm/tests/.kunitconfig
> 
> Changes in v2:
> - Drop an unused variable, that was pointed out by the kernel robot.
> 
>   drivers/gpu/drm/tests/drm_format_helper_test.c | 7 +++++--
>   1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/tests/drm_format_helper_test.c b/drivers/gpu/drm/tests/drm_format_helper_test.c
> index 9536829c6e3a..84b5cc29c8fc 100644
> --- a/drivers/gpu/drm/tests/drm_format_helper_test.c
> +++ b/drivers/gpu/drm/tests/drm_format_helper_test.c
> @@ -409,12 +409,15 @@ static size_t conversion_buf_size(u32 dst_format, unsigned int dst_pitch,
>   				  const struct drm_rect *clip)
>   {
>   	const struct drm_format_info *dst_fi = drm_format_info(dst_format);
> +	unsigned int bpp;
>   
>   	if (!dst_fi)
>   		return -EINVAL;
>   
> -	if (!dst_pitch)
> -		dst_pitch = drm_rect_width(clip) * dst_fi->cpp[0];
> +	if (!dst_pitch) {
> +		bpp = drm_format_info_bpp(dst_fi, 0);
> +		dst_pitch = DIV_ROUND_UP(drm_rect_width(clip) * bpp, 8);
> +	}
>   
>   	return dst_pitch * drm_rect_height(clip);
>   }