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

[Emil Velikov]

Hi Dan,

On 22 July 2017 at 09:00, Daniel Stone <daniel at fooishbar.org> wrote:
> Hi Emil,
>
> On 21 July 2017 at 15:23, Emil Velikov <emil.l.velikov at gmail.com> wrote:
>> I think the key issue is that the resource_get_handle() calls lack
>> proper error handling.
>>
>> There's a single case, that was fixed not too long ago, yet everywhere
>> else we consider that resource_get_handle() can fail.
>> Can we address that instead? Only dri2_query_image seems to be buggy.
>
> 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?
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.

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

-Emil