On Wed, Jan 28, 2026 at 07:25:28PM +0200, Tomi Valkeinen wrote:
> Add greyscale Y8 format.
>
> The 8-bit greyscale format has been discussed before, and the earlier
> guidance was to use DRM_FORMAT_R8, as a single-channel 8-bit pixel.
>
> However, adding DRM_FORMAT_Y8 makes sense, we can mark it as 'is_yuv' in
> the drm_format_info, and this can help the drivers handle e.g.
> full/limited range. This will distinguish two single-channel formats:
> R8, which is a RGB format with the same value for all components, and
> Y8, which is a Y-only YCbCr format, with Cb and Cr being neutral.
>
> Acked-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
> Reviewed-by: Pekka Paalanen <pekka.paalanen@collabora.com>
> Reviewed-by: Vishal Sagar <vishal.sagar@amd.com>
> Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> ---
> drivers/gpu/drm/drm_fourcc.c | 1 +
> include/uapi/drm/drm_fourcc.h | 9 +++++++++
> 2 files changed, 10 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_fourcc.c b/drivers/gpu/drm/drm_fourcc.c
> index b22ef86428a1..a39b9d7a5b62 100644
> --- a/drivers/gpu/drm/drm_fourcc.c
> +++ b/drivers/gpu/drm/drm_fourcc.c
> @@ -275,6 +275,7 @@ const struct drm_format_info *__drm_format_info(u32 format)
> { .format = DRM_FORMAT_YVU422, .depth = 0, .num_planes = 3, .cpp = { 1, 1, 1 }, .hsub = 2, .vsub = 1, .is_yuv = true },
> { .format = DRM_FORMAT_YUV444, .depth = 0, .num_planes = 3, .cpp = { 1, 1, 1 }, .hsub = 1, .vsub = 1, .is_yuv = true },
> { .format = DRM_FORMAT_YVU444, .depth = 0, .num_planes = 3, .cpp = { 1, 1, 1 }, .hsub = 1, .vsub = 1, .is_yuv = true },
> + { .format = DRM_FORMAT_Y8, .depth = 8, .num_planes = 1, .cpp = { 1, 0, 0 }, .hsub = 1, .vsub = 1, .is_yuv = true },
> { .format = DRM_FORMAT_NV12, .depth = 0, .num_planes = 2, .cpp = { 1, 2, 0 }, .hsub = 2, .vsub = 2, .is_yuv = true },
> { .format = DRM_FORMAT_NV21, .depth = 0, .num_planes = 2, .cpp = { 1, 2, 0 }, .hsub = 2, .vsub = 2, .is_yuv = true },
> { .format = DRM_FORMAT_NV16, .depth = 0, .num_planes = 2, .cpp = { 1, 2, 0 }, .hsub = 2, .vsub = 1, .is_yuv = true },
> diff --git a/include/uapi/drm/drm_fourcc.h b/include/uapi/drm/drm_fourcc.h
> index 6c786701238e..e4451668499a 100644
> --- a/include/uapi/drm/drm_fourcc.h
> +++ b/include/uapi/drm/drm_fourcc.h
> @@ -459,6 +459,15 @@ extern "C" {
> #define DRM_FORMAT_YUV444 fourcc_code('Y', 'U', '2', '4') /* non-subsampled Cb (1) and Cr (2) planes */
> #define DRM_FORMAT_YVU444 fourcc_code('Y', 'V', '2', '4') /* non-subsampled Cr (1) and Cb (2) planes */
>
> +/*
> + * Y-only (greyscale) formats
> + *
> + * The Y-only formats are handled similarly to the YCbCr formats in the display
> + * pipeline, with the Cb and Cr implicitly neutral (0.0 in nominal values). This
> + * also means that COLOR_RANGE property applies to the Y-only formats.
> + */
> +
> +#define DRM_FORMAT_Y8 fourcc_code('G', 'R', 'E', 'Y') /* 8-bit Y-only */
>
> /*
> * Format Modifiers:
--
Regards,
Laurent Pinchart