[Mesa-dev] [PATCH 2/3] st/dri2: Return invalid modifier when no driver support

[Daniel Stone]

Hi,

On 24 July 2017 at 12:30, Emil Velikov <emil.l.velikov at gmail.com> wrote:
> On 22 July 2017 at 09:00, Daniel Stone <daniel at fooishbar.org> wrote:
>> We can address that as well, but not instead. Drivers which aren't
>> aware of modifiers will return success (as they know how to export
>> KMS-type handles), but not initialise the modifier field (because they
>> aren't aware of it). So we can check for failure, but the case I was
>> seeing here is that resource_get_handle() was succeeding - else we
>> wouldn't have had a buffer to query modifiers on in the first place -
>> but failing to either give the correct modifier or INVALID.
>>
> You're right - my suggestion seems orthogonal to the issue at hand.
>
> At the same time if the driver does not support modifiers, we should
> return false for the query, shouldn't we?

Indeed, it should. Unfortunately, there's no explicit query for
modifier: we just expect the driver to set whandle.modifier when we do
a KMS handle query. Or, in this case, not set it. I didn't easily see
a query interface we could use to support this.

> The egl/wayland will need an update code to correctly handle the
> queryImage failure (sorry for missing that earlier), falling back to
> wl_drm.
> GBM already has similar checks/fallback paths.

I can do that.

> AFAICT that will make the check in 1/3 unreachable, yet still nice to have.

I don't really see how? 1/3 is for when we have zwp_linux_dmabuf_v1
support in the Wayland compositor, but it fails to advertise any
modifiers for the formats we're interested in.

Cheers,
Daniel