[PATCH 1/2] drm/fourcc: add ARM tiled format modifier

[Brian Starkey]

Hi,

On Wed, Feb 06, 2019 at 09:14:56PM +0800, Qiang Yu wrote:
> Signed-off-by: Qiang Yu <yuq825 at gmail.com>
> ---
>  include/uapi/drm/drm_fourcc.h | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/include/uapi/drm/drm_fourcc.h b/include/uapi/drm/drm_fourcc.h
> index 0b44260a5ee9..953b59eb3fd2 100644
> --- a/include/uapi/drm/drm_fourcc.h
> +++ b/include/uapi/drm/drm_fourcc.h
> @@ -644,6 +644,15 @@ extern "C" {
>   */
>  #define AFBC_FORMAT_MOD_SC      (1ULL <<  9)
>  
> +/*
> + * ARM tiled format
> + *
> + * This is used by ARM Mali Utgard/Midgard GPU. It divides buffer into
> + * 16x16 pixel blocks. Blocks are stored linearly in order, but pixels
> + * in the block are reordered.
> + */
> +#define DRM_FORMAT_MOD_ARM_TILED fourcc_mod_code(ARM, 1)
> +

This conflicts with the already-defined AFBC modifiers. It has the
same value as:

DRM_FORMAT_MOD_ARM_AFBC(AFBC_FORMAT_MOD_BLOCK_SIZE_16x16);

I would suggest we use the top bit(s) to namespace between the
different types of tiling formats Arm has (e.g. AFBC vs
non-compressed).

I think this would be an internal-only layout though. Do we need
modifiers for internal-only formats? I thought they were mainly for
sharing cross-device. I also didn't see this macro getting used
anywhere in the driver; I suppose at a minimum you should validate the
modifier value provided by userspace.

Thanks,
-Brian

>  #if defined(__cplusplus)
>  }
>  #endif
> -- 
> 2.17.1
> 
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