Hi Dave, On 31/10/2022 13:27, Dave Stevenson wrote: > Hi Hans & Sakari > > A question raised from review of [1]: > > Is it correct that any subdevice driver that supports any controls > should advertise V4L2_SUBDEV_FL_HAS_EVENTS and have > subscribe_event/unsubscribe_event core_ops? > > I added that patch for ov9282 to resolve a v4l2-compliance failure: > fail: v4l2-test-controls.cpp(835): subscribe event for control 'User > Controls' failed > test VIDIOC_(UN)SUBSCRIBE_EVENT/DQEVENT: FAIL > but it surprised Jacopo, and he has observed that many of the current > drivers with controls don't meet this requirement. > > I just wanted confirmation from those in the know. It should only be needed if V4L2_SUBDEV_FL_HAS_DEVNODE is also set in the subdev driver. If HAS_DEVNODE is set, and there are controls, then HAS_EVENTS must be set and you have to be able to (un)subscribe to events. Because the controls can be exposed to userspace via a v4l-subdevX device, and userspace has to be able to subscribe to control events so that it is notified when the control changes value. The compliance testing of v4l-subdev devices isn't that old, so a lot of older subdev drivers where never checked for compliance. Regards, Hans > > Thanks > Dave > > [1] https://patchwork.linuxtv.org/project/linux-media/patch/20221005152809.3785786-17-dave.stevenson@xxxxxxxxxxxxxxx/
