Re: [PATCH] RFC: drm: add support for tiled/compressed/etc modifier in addfb2 (v1.5)

Tvrtko Ursulin
2015-01-28T17:57:56Z

On 01/28/2015 05:37 PM, Daniel Vetter wrote:
> From: Rob Clark <robdclark@gmail.com>
>
> In DRM/KMS we are lacking a good way to deal with tiled/compressed
> formats. Especially in the case of dmabuf/prime buffer sharing, where
> we cannot always rely on under-the-hood flags passed to driver specific
> gem-create ioctl to pass around these extra flags.
>
> The proposal is to add a per-plane format modifier. This allows to, if
> necessary, use different tiling patters for sub-sampled planes, etc.
> The format modifiers are added at the end of the ioctl struct, so for
> legacy userspace it will be zero padded.
>
> TODO how best to deal with assignment of modifier token values? The
> rough idea was to namespace things with an 8bit vendor-id, and then
> beyond that it is treated as an opaque value. But that was a relatively
> arbitrary choice. There are cases where same tiling pattern and/or
> compression is supported by various different vendors. So we should
> standardize to use the vendor-id and value of the first one who
> documents the format?

Maybe:
__u64 modifier[4];
__u64 vendor_modifier[4];

?

Regards,

Tvrtko