Adding the wayland-devel list for Wayland compositor developers.
Also adding the mesa-dev list for Mesa developers, though note that this list
isn't really active anymore. You might want to create an MR or Gitlab issue to
get feedback from Mesa developers.
On 2/17/26 11:29, Christian König wrote:
>>
>> @@ -732,6 +732,8 @@ static const struct drm_ioctl_desc drm_ioctls[] = {
>> DRM_IOCTL_DEF(DRM_IOCTL_MODE_LIST_LESSEES, drm_mode_list_lessees_ioctl,
>> DRM_MASTER),
>> DRM_IOCTL_DEF(DRM_IOCTL_MODE_GET_LEASE, drm_mode_get_lease_ioctl,
>> DRM_MASTER),
>> DRM_IOCTL_DEF(DRM_IOCTL_MODE_REVOKE_LEASE, drm_mode_revoke_lease_ioctl,
>> DRM_MASTER),
>> + DRM_IOCTL_DEF(DRM_IOCTL_SYNCOBJ_QUERY_ERROR,
>> drm_syncobj_query_error_ioctl,
>> + DRM_RENDER_ALLOW),
>
> My educated guess is that userspace doesn't want to call this IOCTL
> separately because of performance reasons.
>
> Instead add some additional flag to DRM_SYNCOBJ_WAIT_FLAGS_* so that the
> IOCTL aborts the wait and returns an error as soon as it sees any fence with
> an error.
>
> Another DRM_SYNCOBJ_QUERY_FLAGS_* is potentially also useful to query the
> error on a number of drm_syncobjs at the same time.
>
> But in general since this is not a HW feature the userspace developers need
> to voice their requirements and explain how they want to have that
> implemented.
mutter currently doesn't use the syncobj-specific ioctls to wait for a syncobj
(timeline point) to signal / check if it has. Instead, it uses
drmSyncobjEventfd / drmSyncobjExportSyncFile to get an eventfd / sync_file
representing the timeline point / fence, then checks the status of the fd and
waits for it to signal using generic poll()-style functionality. So unless the
error condition can be communicated via the latter (and plumbed through glib
APIs), mutter would need to check for fence errors separately.
Xwayland uses drmSyncobjTimelineWait to check if a syncobj timeline point has a
fence / has signalled, it also uses drmSyncobjEventfd similarly to mutter
though.
--
Earthling Michel Dänzer \ GNOME / Xwayland / Mesa developer
https://redhat.com \ Libre software enthusiast
