[PATCH 1/2] drm: Add new DRM_IOCTL_MODE_GETPLANE2

[Daniel Stone]

Hi,

On 1 April 2017 at 19:47, Rob Clark <robdclark at gmail.com> wrote:
> On Tue, Dec 20, 2016 at 7:12 PM, Kristian H. Kristensen
> <hoegsberg at gmail.com> wrote:
>> This new ioctl exctends DRM_IOCTL_MODE_GETPLANE, by returning
>> information about the modifiers that will work with each format.
>
> So, just to toss out a completely different idea..
>
> What if instead of a new ioctl, we had a read-only blob property
> (which encoded the info basically the same way, plus the fourcc's)?
>
> If we do writeback via some sort of OUT_FB_ID property on plane/crtc,
> we will need the same sort of format information so userspace knows
> what output formats (and modifiers) are supported.  So re-using the
> same blob property layout (and userspace parsing) seems useful.

I'd definitely be cool with this. It doesn't make our lives any easier
or more difficult in terms of parsing, and it also avoids a dep on new
libdrm API/ABI, which is always nice. If anyone types this up, I'll
happily port the Weston WIP.

Cheers,
Daniel