Hi,
On 28/01/2026 13:49, Laurent Pinchart wrote:
> Hi Tomi,
>
> Thank you for the patch.
>
> 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...
Tomi
