[PATCH] drm: drm_fourcc: add 10/12bit software decoder YCbCr formats

[Robert Mader]

Hey Laurent, thanks for the feedback!

On 24.04.25 15:31, Laurent Pinchart wrote:
> On Thu, Apr 24, 2025 at 02:53:18PM +0200, Robert Mader wrote:
>> Chris, Javier, Laurent - sorry for the noise, but given you reviewed
>> changes in the respective files before, maybe you can help me moving
>> this forward? I'd be very happy for any feedback to get this landed,
>> thanks! :)
> I don't have spare bandwidth at the moment, sorry :-( One comment below
> though.
>
> Tomi, can you check if there's any overlap with the formats you're
> adding for the Xilinx FPGA drivers ?
>
>> On 07.04.25 21:13, Robert Mader wrote:
>>> This adds FOURCCs for 10/12bit YCbCr formats used by software decoders
>>> like ffmpeg, dav1d and libvpx. The intended use-case is buffer sharing
>>> between SW-decoders and GPUs by allocating buffers with udmabuf or
>>> dma-heaps, avoiding unnecessary copies or format conversions.
>>>
>>> Unlike formats typically used by hardware decoders these formats
>>> use a LSB alignment. In order to allow fast implementations in GL
>>> and Vulkan the padding must contain only zeros, so the float
>>> representation can calculated by simple multiplicating with 2^6=64
>>> or 2^4=16.
> This needs to be documented somewhere.
Ok, will add a short comment in the description.
>
>>> WIP MRs for Mesa, Vulkan and Gstreamer can be found at:
>>>    - https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/34303
>>>    - https://github.com/rmader/Vulkan-Docs/commits/ycbcr-16bit-lsb-formats/
>>>    - https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/8540
>>>
>>> The values where inspired by the corresponding VA_FOURCC_I010, however
>>> suggestions are very welcome.
>>>
>>> Signed-off-by: Robert Mader <robert.mader at collabora.com>
>>> ---
>>>    drivers/gpu/drm/drm_fourcc.c  | 18 ++++++++++++++++++
>>>    include/uapi/drm/drm_fourcc.h | 20 ++++++++++++++++++++
>>>    2 files changed, 38 insertions(+)
>>>
>>> diff --git a/drivers/gpu/drm/drm_fourcc.c b/drivers/gpu/drm/drm_fourcc.c
>>> index 3a94ca211f9c..917f77703645 100644
>>> --- a/drivers/gpu/drm/drm_fourcc.c
>>> +++ b/drivers/gpu/drm/drm_fourcc.c
>>> @@ -346,6 +346,24 @@ const struct drm_format_info *__drm_format_info(u32 format)
>>>    		{ .format = DRM_FORMAT_P030,            .depth = 0,  .num_planes = 2,
>>>    		  .char_per_block = { 4, 8, 0 }, .block_w = { 3, 3, 0 }, .block_h = { 1, 1, 0 },
>>>    		  .hsub = 2, .vsub = 2, .is_yuv = true},
>>> +		{ .format = DRM_FORMAT_I010,            .depth = 0,  .num_planes = 3,
>>> +		  .char_per_block = { 2, 2, 2 }, .block_w = { 1, 1, 1 }, .block_h = { 1, 1, 1 },
>>> +		  .hsub = 2, .vsub = 2, .is_yuv = true},
>>> +		{ .format = DRM_FORMAT_I210,            .depth = 0,  .num_planes = 3,
>>> +		  .char_per_block = { 2, 2, 2 }, .block_w = { 1, 1, 1 }, .block_h = { 1, 1, 1 },
>>> +		  .hsub = 2, .vsub = 1, .is_yuv = true},
>>> +		{ .format = DRM_FORMAT_I410,            .depth = 0,  .num_planes = 3,
>>> +		  .char_per_block = { 2, 2, 2 }, .block_w = { 1, 1, 1 }, .block_h = { 1, 1, 1 },
>>> +		  .hsub = 1, .vsub = 1, .is_yuv = true},
>>> +		{ .format = DRM_FORMAT_I012,            .depth = 0,  .num_planes = 3,
>>> +		  .char_per_block = { 2, 2, 2 }, .block_w = { 1, 1, 1 }, .block_h = { 1, 1, 1 },
>>> +		  .hsub = 2, .vsub = 2, .is_yuv = true},
>>> +		{ .format = DRM_FORMAT_I212,            .depth = 0,  .num_planes = 3,
>>> +		  .char_per_block = { 2, 2, 2 }, .block_w = { 1, 1, 1 }, .block_h = { 1, 1, 1 },
>>> +		  .hsub = 2, .vsub = 1, .is_yuv = true},
>>> +		{ .format = DRM_FORMAT_I412,            .depth = 0,  .num_planes = 3,
>>> +		  .char_per_block = { 2, 2, 2 }, .block_w = { 1, 1, 1 }, .block_h = { 1, 1, 1 },
>>> +		  .hsub = 1, .vsub = 1, .is_yuv = true},
>>>    	};
>>>    
>>>    	unsigned int i;
>>> diff --git a/include/uapi/drm/drm_fourcc.h b/include/uapi/drm/drm_fourcc.h
>>> index e41a3cec6a9e..f22c80031595 100644
>>> --- a/include/uapi/drm/drm_fourcc.h
>>> +++ b/include/uapi/drm/drm_fourcc.h
>>> @@ -397,6 +397,26 @@ 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 */
>>>    
>>> +/*
>>> + * 3 plane YCbCr LSB aligned
>>> + * index 0 = Y plane, [15:0] x:Y [6:10] little endian
>>> + * index 1 = Cr plane, [15:0] x:Cr [6:10] little endian
>>> + * index 2 = Cb plane, [15:0] x:Cb [6:10] little endian
>>> + */
>>> +#define DRM_FORMAT_I010	fourcc_code('I', '0', '1', '0') /* 2x2 subsampled Cb (1) and Cr (2) planes 10 bits per channel */
>>> +#define DRM_FORMAT_I210	fourcc_code('I', '2', '1', '0') /* 2x1 subsampled Cb (1) and Cr (2) planes 10 bits per channel */
>>> +#define DRM_FORMAT_I410	fourcc_code('I', '4', '1', '0') /* non-subsampled Cb (1) and Cr (2) planes 10 bits per channel */
>>> +
>>> +/*
>>> + * 3 plane YCbCr LSB aligned
>>> + * index 0 = Y plane, [15:0] x:Y [4:12] little endian
>>> + * index 1 = Cr plane, [15:0] x:Cr [4:12] little endian
>>> + * index 2 = Cb plane, [15:0] x:Cb [4:12] little endian
>>> + */
>>> +#define DRM_FORMAT_I012	fourcc_code('I', '0', '1', '2') /* 2x2 subsampled Cb (1) and Cr (2) planes 12 bits per channel */
>>> +#define DRM_FORMAT_I212	fourcc_code('I', '2', '1', '2') /* 2x1 subsampled Cb (1) and Cr (2) planes 12 bits per channel */
>>> +#define DRM_FORMAT_I412	fourcc_code('I', '4', '1', '2') /* non-subsampled Cb (1) and Cr (2) planes 12 bits per channel */
>>> +
>>>    
>>>    /*
>>>     * Format Modifiers: