Ben Widawsky benjamin.widawsky at intel.com
Tue Apr 4 19:41:14 UTC 2017

On 17-04-04 11:07:26, Daniel Stone wrote:
>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.

Okay. Sounds like we have consensus. I'm working on it now. I think like Rob
said on IRC, a good amount of it will be reusable from GET_PLANE2. I'm a bit new
to the binary blob props, so if anyone has a strong opinion on how it should
look, please speak now. Otherwise, I'll just wire up something.

Ben Widawsky, Intel Open Source Technology Center

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