On Wed, Jan 28, 2026 at 05:38:11PM +0200, Tomi Valkeinen wrote: > On 28/01/2026 13:49, Laurent Pinchart wrote: > > On Mon, Dec 01, 2025 at 02:18:45PM +0200, Tomi Valkeinen wrote: > >> Add greyscale Y8 format. > > > > I would explain here why we need a new format and can't just use > > DRM_FORMAT_R8. You don't need to convince me, but I think it's important > > to summarize the rationale should someone later wonder why we introduced > > this. > > > >> Acked-by: Dmitry Baryshkov <[email protected]> > >> Reviewed-by: Pekka Paalanen <[email protected]> > >> Reviewed-by: Vishal Sagar <[email protected]> > >> Signed-off-by: Tomi Valkeinen <[email protected]> > >> --- > >> drivers/gpu/drm/drm_fourcc.c | 1 + > >> include/uapi/drm/drm_fourcc.h | 10 ++++++++++ > >> 2 files changed, 11 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..5cfc188c4e72 100644 > >> --- a/include/uapi/drm/drm_fourcc.h > >> +++ b/include/uapi/drm/drm_fourcc.h > >> @@ -459,6 +459,16 @@ 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. > >> + * > > > > Extra blank line. > > I'll drop. > > >> + */ > >> + > >> +#define DRM_FORMAT_Y8 fourcc_code('G', 'R', 'E', 'Y') /* > >> 8-bit Y-only */ > > > > I would have gone for 'Y', '8', ' ', ' ' > > Missed these comments earlier... > > Yes, "Y8 " makes sense. But I was trying to be nice, as there are > already users for Y8 ("GREY") with BSP kernels, and changing the fourcc > code would break their userspace...
That's a more compeling argument than matching the V4L2 4CC. I have a slight preference for 'Y8 ' for how it would appear in debug messages, but I'm also fine being nice :-) Reviewed-by: Laurent Pinchart <[email protected]> -- Regards, Laurent Pinchart
