Re: [PATCH RFC v3 4/6] drm: drm_fourcc: Add new formats for Xilinx IPs

[Daniel Vetter <daniel@ffwll.ch>]

On Fri, Feb 09, 2018 at 05:35:54PM -0800, Hyun Kwon wrote:
> This patch adds new formats needed by Xilinx IP. Pixels are not
> byte-aligned in these formats, and the drm_format_info for these
> formats has macro-pixel information.
> 
> Signed-off-by: Jeffrey Mouroux <jmouroux@xilinx.com>
> Signed-off-by: Hyun Kwon <hyun.kwon@xilinx.com>
> ---
> v3
> - Update entries for changes
> - Squash fourcc patch into this
> v2
> - Add detailed descriptions
> - Remove formats with no user
> ---
> ---
>  drivers/gpu/drm/drm_fourcc.c  | 2 ++
>  include/uapi/drm/drm_fourcc.h | 8 ++++++++
>  2 files changed, 10 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_fourcc.c b/drivers/gpu/drm/drm_fourcc.c
> index ed95de2..36bff7a 100644
> --- a/drivers/gpu/drm/drm_fourcc.c
> +++ b/drivers/gpu/drm/drm_fourcc.c
> @@ -168,6 +168,8 @@ const struct drm_format_info *__drm_format_info(u32 format)
>  		{ .format = DRM_FORMAT_NV61,		.depth = 0,  .num_planes = 2, .cpp = { 1, 2, 0 }, .hsub = 2, .vsub = 1 },
>  		{ .format = DRM_FORMAT_NV24,		.depth = 0,  .num_planes = 2, .cpp = { 1, 2, 0 }, .hsub = 1, .vsub = 1 },
>  		{ .format = DRM_FORMAT_NV42,		.depth = 0,  .num_planes = 2, .cpp = { 1, 2, 0 }, .hsub = 1, .vsub = 1 },
> +		{ .format = DRM_FORMAT_XV15,		.depth = 0,  .num_planes = 2, .pixels_per_macropixel = { 3, 3, 0 }, .bytes_per_macropixel = { 4, 8, 0 }, .hsub = 2, .vsub = 2, },
> +		{ .format = DRM_FORMAT_XV20,		.depth = 0,  .num_planes = 2, .pixels_per_macropixel = { 3, 3, 0 }, .bytes_per_macropixel = { 4, 8, 0 }, .hsub = 2, .vsub = 1, },

There's no need to set fields explicitly to 0. I think we could even do a
separate patch to nuke all the .depth = 0, assignments.

One thing that I've realized now that your new pixel formats stick out:
How is macropixel supposed to interact with hsub/vsub? From you example it
looks like macropixels are applied after subsampling (i.e. a macropixel
block of 3 pixels, but hsub = 2 means the macroblock will actually span 6
pixels). I think the kerneldoc in the earlier patch should explain this is
allowed, and how it's supposed to work exactly.

Also, do we have open-source userspace somewhere for this new pixel format?

Thanks, Daniel


>  		{ .format = DRM_FORMAT_YUYV,		.depth = 0,  .num_planes = 1, .cpp = { 2, 0, 0 }, .hsub = 2, .vsub = 1 },
>  		{ .format = DRM_FORMAT_YVYU,		.depth = 0,  .num_planes = 1, .cpp = { 2, 0, 0 }, .hsub = 2, .vsub = 1 },
>  		{ .format = DRM_FORMAT_UYVY,		.depth = 0,  .num_planes = 1, .cpp = { 2, 0, 0 }, .hsub = 2, .vsub = 1 },
> diff --git a/include/uapi/drm/drm_fourcc.h b/include/uapi/drm/drm_fourcc.h
> index e04613d..6ac5282 100644
> --- a/include/uapi/drm/drm_fourcc.h
> +++ b/include/uapi/drm/drm_fourcc.h
> @@ -142,6 +142,14 @@ extern "C" {
>  #define DRM_FORMAT_NV42		fourcc_code('N', 'V', '4', '2') /* non-subsampled Cb:Cr plane */
>  
>  /*
> + * 2 plane 10 bit per component YCbCr
> + * index 0 = Y plane, [31:0] x:Y2:Y1:Y0 2:10:10:10 little endian
> + * index 1 = Cb:Cr plane, [63:0] x:Cb2:Cr2:Cb1:x:Cr1:Cb0:Cr0 2:10:10:10:2:10:10:10 little endian
> + */
> +#define DRM_FORMAT_XV15		fourcc_code('X', 'V', '1', '5') /* 2x2 subsampled Cb:Cr plane 2:10:10:10 */
> +#define DRM_FORMAT_XV20		fourcc_code('X', 'V', '2', '0') /* 2x1 subsampled Cb:Cr plane 2:10:10:10 */
> +
> +/*
>   * 3 plane YCbCr
>   * index 0: Y plane, [7:0] Y
>   * index 1: Cb plane, [7:0] Cb
> -- 
> 2.7.4
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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