2020-10-07 10:09:03

by Daniel Vetter

Subject: Re: [PATCH] drm/fourcc: Add AXBXGXRX106106106106 format

On Wed, Oct 7, 2020 at 11:29 AM Matteo Franchin <[email protected]> wrote:
>
> Add ABGR format with 10-bit components packed in 64-bit per pixel.
> This format can be used to handle
> VK_FORMAT_R10X6G10X6B10X6A10X6_UNORM_4PACK16 on little-endian
> architectures.
>
> Signed-off-by: Matteo Franchin <[email protected]>

So is this essentially 16 bit, with the lowest 6 bits in each channel
ignored? What exactly is this used for where the full 16bit format
doesn't work?
-Daniel

> ---
> drivers/gpu/drm/drm_fourcc.c | 1 +
> include/uapi/drm/drm_fourcc.h | 7 +++++++
> 2 files changed, 8 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_fourcc.c b/drivers/gpu/drm/drm_fourcc.c
> index 722c7ebe4e88..bba03fcb016d 100644
> --- a/drivers/gpu/drm/drm_fourcc.c
> +++ b/drivers/gpu/drm/drm_fourcc.c
> @@ -202,6 +202,7 @@ const struct drm_format_info *__drm_format_info(u32 format)
> { .format = DRM_FORMAT_XBGR16161616F, .depth = 0, .num_planes = 1, .cpp = { 8, 0, 0 }, .hsub = 1, .vsub = 1 },
> { .format = DRM_FORMAT_ARGB16161616F, .depth = 0, .num_planes = 1, .cpp = { 8, 0, 0 }, .hsub = 1, .vsub = 1, .has_alpha = true },
> { .format = DRM_FORMAT_ABGR16161616F, .depth = 0, .num_planes = 1, .cpp = { 8, 0, 0 }, .hsub = 1, .vsub = 1, .has_alpha = true },
> + { .format = DRM_FORMAT_AXBXGXRX106106106106, .depth = 0, .num_planes = 1, .cpp = { 8, 0, 0 }, .hsub = 1, .vsub = 1, .has_alpha = true },
> { .format = DRM_FORMAT_RGB888_A8, .depth = 32, .num_planes = 2, .cpp = { 3, 1, 0 }, .hsub = 1, .vsub = 1, .has_alpha = true },
> { .format = DRM_FORMAT_BGR888_A8, .depth = 32, .num_planes = 2, .cpp = { 3, 1, 0 }, .hsub = 1, .vsub = 1, .has_alpha = true },
> { .format = DRM_FORMAT_XRGB8888_A8, .depth = 32, .num_planes = 2, .cpp = { 4, 1, 0 }, .hsub = 1, .vsub = 1, .has_alpha = true },
> diff --git a/include/uapi/drm/drm_fourcc.h b/include/uapi/drm/drm_fourcc.h
> index 82f327801267..76eedba52b77 100644
> --- a/include/uapi/drm/drm_fourcc.h
> +++ b/include/uapi/drm/drm_fourcc.h
> @@ -155,6 +155,13 @@ extern "C" {
> #define DRM_FORMAT_ARGB16161616F fourcc_code('A', 'R', '4', 'H') /* [63:0] A:R:G:B 16:16:16:16 little endian */
> #define DRM_FORMAT_ABGR16161616F fourcc_code('A', 'B', '4', 'H') /* [63:0] A:B:G:R 16:16:16:16 little endian */
>
> +/*
> + * RGBA format with 10-bit components packed in 64-bit per pixel, with 6 bits
> + * of unused padding per component:
> + * [63:0] A:x:B:x:G:x:R:x 10:6:10:6:10:6:10:6 little endian
> + */
> +#define DRM_FORMAT_AXBXGXRX106106106106 fourcc_code('A', 'B', '1', '0')
> +
> /* packed YCbCr */
> #define DRM_FORMAT_YUYV fourcc_code('Y', 'U', 'Y', 'V') /* [31:0] Cr0:Y1:Cb0:Y0 8:8:8:8 little endian */
> #define DRM_FORMAT_YVYU fourcc_code('Y', 'V', 'Y', 'U') /* [31:0] Cb0:Y1:Cr0:Y0 8:8:8:8 little endian */
> --
> 2.17.1
>


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

2020-10-07 17:06:59

by Matteo Franchin

Subject: Re: [PATCH] drm/fourcc: Add AXBXGXRX106106106106 format

Hi Daniel,

On Wed, Oct 07, 2020 at 12:06:34PM +0200, Daniel Vetter wrote:
> On Wed, Oct 7, 2020 at 11:29 AM Matteo Franchin <[email protected]> wrote:
> >
> > Add ABGR format with 10-bit components packed in 64-bit per pixel.
> > This format can be used to handle
> > VK_FORMAT_R10X6G10X6B10X6A10X6_UNORM_4PACK16 on little-endian
> > architectures.
> >
> > Signed-off-by: Matteo Franchin <[email protected]>
>
> So is this essentially 16 bit, with the lowest 6 bits in each channel
> ignored? What exactly is this used for where the full 16bit format
> doesn't work?

If you are asking why we don't add a 16-bit format, instead (e.g.
DRM_FORMAT_ABGR16161616) the answer is that this is really a 10-bit
format: only the 10 MSBs are preserved.

We'd be uncomfortable to add support for a 16-bit format and just
ignore the lowest 6 bits.

Thanks,
Matteo


> -Daniel
>
> > ---
> > drivers/gpu/drm/drm_fourcc.c | 1 +
> > include/uapi/drm/drm_fourcc.h | 7 +++++++
> > 2 files changed, 8 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/drm_fourcc.c b/drivers/gpu/drm/drm_fourcc.c
> > index 722c7ebe4e88..bba03fcb016d 100644
> > --- a/drivers/gpu/drm/drm_fourcc.c
> > +++ b/drivers/gpu/drm/drm_fourcc.c
> > @@ -202,6 +202,7 @@ const struct drm_format_info *__drm_format_info(u32 format)
> > { .format = DRM_FORMAT_XBGR16161616F, .depth = 0, .num_planes = 1, .cpp = { 8, 0, 0 }, .hsub = 1, .vsub = 1 },
> > { .format = DRM_FORMAT_ARGB16161616F, .depth = 0, .num_planes = 1, .cpp = { 8, 0, 0 }, .hsub = 1, .vsub = 1, .has_alpha = true },
> > { .format = DRM_FORMAT_ABGR16161616F, .depth = 0, .num_planes = 1, .cpp = { 8, 0, 0 }, .hsub = 1, .vsub = 1, .has_alpha = true },
> > + { .format = DRM_FORMAT_AXBXGXRX106106106106, .depth = 0, .num_planes = 1, .cpp = { 8, 0, 0 }, .hsub = 1, .vsub = 1, .has_alpha = true },
> > { .format = DRM_FORMAT_RGB888_A8, .depth = 32, .num_planes = 2, .cpp = { 3, 1, 0 }, .hsub = 1, .vsub = 1, .has_alpha = true },
> > { .format = DRM_FORMAT_BGR888_A8, .depth = 32, .num_planes = 2, .cpp = { 3, 1, 0 }, .hsub = 1, .vsub = 1, .has_alpha = true },
> > { .format = DRM_FORMAT_XRGB8888_A8, .depth = 32, .num_planes = 2, .cpp = { 4, 1, 0 }, .hsub = 1, .vsub = 1, .has_alpha = true },
> > diff --git a/include/uapi/drm/drm_fourcc.h b/include/uapi/drm/drm_fourcc.h
> > index 82f327801267..76eedba52b77 100644
> > --- a/include/uapi/drm/drm_fourcc.h
> > +++ b/include/uapi/drm/drm_fourcc.h
> > @@ -155,6 +155,13 @@ extern "C" {
> > #define DRM_FORMAT_ARGB16161616F fourcc_code('A', 'R', '4', 'H') /* [63:0] A:R:G:B 16:16:16:16 little endian */
> > #define DRM_FORMAT_ABGR16161616F fourcc_code('A', 'B', '4', 'H') /* [63:0] A:B:G:R 16:16:16:16 little endian */
> >
> > +/*
> > + * RGBA format with 10-bit components packed in 64-bit per pixel, with 6 bits
> > + * of unused padding per component:
> > + * [63:0] A:x:B:x:G:x:R:x 10:6:10:6:10:6:10:6 little endian
> > + */
> > +#define DRM_FORMAT_AXBXGXRX106106106106 fourcc_code('A', 'B', '1', '0')
> > +
> > /* packed YCbCr */
> > #define DRM_FORMAT_YUYV fourcc_code('Y', 'U', 'Y', 'V') /* [31:0] Cr0:Y1:Cb0:Y0 8:8:8:8 little endian */
> > #define DRM_FORMAT_YVYU fourcc_code('Y', 'V', 'Y', 'U') /* [31:0] Cb0:Y1:Cr0:Y0 8:8:8:8 little endian */
> > --
> > 2.17.1
> >
>
>
> --
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch
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