[Intel-gfx] [PATCH 1/3] drm: Add new DRM_IOCTL_MODE_GETPLANE2

[Daniel Stone]

Hi,

On 12 January 2017 at 18:11, Ville Syrjälä
<ville.syrjala at linux.intel.com> wrote:
> On Thu, Jan 12, 2017 at 05:50:15PM +0000, Daniel Stone wrote:
>> struct drm_plane {
>>     struct {
>>         uint32_t format;
>>         uint64_t modifiers[];
>>     } formats[];
>> }
>
> Flipping formats[] vs. modifiers[] here would seem like it should make
> this easier with the proposed kernel API. And if the kernel will also
> uarantee that multiple instances of the same modifier must be returned
> contiguously, then it should be even easier.
>
> Oh and flipping formats[] and modifiers[] should also save a quite a
> bit of space since each format takes twice as much space as each
> modifier. But I suppose that might come at a runtime cost if you have
> to look for a specific format in each modifier's format list instead
> of having to look at just the modifier list of a specific format. So
> I suppose not flipping might be better after all, which I guess would
> complicate populating the infromation somewhat.
>
> Anyways, that's all a bit unrelated to the matter at hand, so I'll stop
> now and just state that I don't mind having an explicit offset if
> people really want it.

It would make sense, but then gbm_surface_create_with_modifiers takes
a fixed pixel format and a list of acceptable modifiers (which to me
seems like the right way around as an API), so whenever I was creating
a surface, I'd have to walk through and create a new list, flipped
back the other way.

Cheers,
Daniel