Re: [PATCH v2] drm/fourcc: Add Apple Interchange layout format modifier

[Alyssa Rosenzweig]

The one big missing piece here is how strides are defined. I assume from
context it's the same convention as GPU_TILED_COMPRESSED but this should
probably be spelled out.

Just adding a sentence "Strides follow the same convention
as DRM_FORMAT_MOD_APPLE_GPU_TILED." should be enough to define the uAPI
unambiguously here. With that it will be

Reviewed-by: Alyssa Rosenzweig <alyssa@xxxxxxxxx>

Le Sun, Oct 04, 2026 at 10:42:29PM +1000, James Calligeros a écrit :
> Apple Interchange is a tiled and compressed image layout used
> for buffer exchange between Apple hardware blocks. It is
> similar to the already-supported GPU_TILED_COMPRESSED layout.
> 
> Add a format modifier for Apple Interchange so that it can be
> used for buffer exchange.
> 
> Signed-off-by: James Calligeros <jcalligeros99@xxxxxxxxx>
> ---
> Changes in v2:
> - Fix typo
> - Link to v1: https://patch.msgid.link/20260831-apple-interchange-modifier-v1-1-5d6e27f9f308@xxxxxxxxx
> 
> To: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx>
> To: Maxime Ripard <mripard@xxxxxxxxxx>
> To: Thomas Zimmermann <tzimmermann@xxxxxxx>
> To: David Airlie <airlied@xxxxxxxxx>
> To: Simona Vetter <simona@xxxxxxxx>
> Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> ---
>  include/uapi/drm/drm_fourcc.h | 20 ++++++++++++++++++++
>  1 file changed, 20 insertions(+)
> 
> diff --git a/include/uapi/drm/drm_fourcc.h b/include/uapi/drm/drm_fourcc.h
> index a103fdc0b3a3..d304ee5c614c 100644
> --- a/include/uapi/drm/drm_fourcc.h
> +++ b/include/uapi/drm/drm_fourcc.h
> @@ -1626,6 +1626,26 @@ drm_fourcc_canonicalize_nvidia_format_mod(__u64 modifier)
>  #define DRM_FORMAT_MOD_APPLE_GPU_TILED fourcc_mod_code(APPLE, 1)
>  #define DRM_FORMAT_MOD_APPLE_GPU_TILED_COMPRESSED fourcc_mod_code(APPLE, 2)
>  
> +/*
> + * Apple Interchange layout
> + *
> + * Apple Interchange is a compressed framebuffer format used exclusively for
> + * sharing buffers between hardware blocks (GPU, display controller, video
> + * codecs) on Apple platforms. It is similar to and uses the same compression
> + * scheme as GPU_TILED_COMPRESSED. There is no known uncompressed variant
> + * of Apple Interchange.
> + *
> + * Unlike the GPU layouts, tile size is not dependent on bit depth. RGB
> + * images and the chroma components of YUV images use 16x16 tiles. The
> + * luma component of YUV images uses 32x32 tiles. Compression tiles
> + * are once again 16x16 with 8 bytes of metadata per compression subtile.
> + *
> + * AGX has limited support for Apple Interchange. It cannot be used for Z/S
> + * buffers or array images, for example. It is intended for scanout buffer
> + * sharing only.
> + */
> +#define DRM_FORMAT_MOD_APPLE_INTERCHANGE fourcc_mod_code(APPLE, 3)
> +
>  /*
>   * AMD modifiers
>   *
> 
> ---
> base-commit: 08dbfad3f5040f5bdb6c529da20d6d4e81fefd72
> change-id: 20260830-apple-interchange-modifier-cbcc311c835d
> 
> Best regards,
> --  
> James Calligeros <jcalligeros99@xxxxxxxxx>
>