Hi Michael, On Wed, Apr 12, 2023 at 03:43:26PM +0200, Michael Riesch wrote: > Hi Sakari, > > On 4/12/23 14:05, Sakari Ailus wrote: > > Hi Michael, > > > > On Wed, Apr 12, 2023 at 01:57:36PM +0200, Michael Riesch wrote: > >> Hi Sakari, > >> > >> On 4/12/23 13:50, Sakari Ailus wrote: > >>> Hi Michael, > >>> > >>> On Wed, Apr 12, 2023 at 10:00:26AM +0200, Michael Riesch wrote: > >>>> - Different controls: If moving = (V4L2_CID_FOCUS_ABSOLUTE == current), > >>>> then what happens if the application performs a > >>>> V4L2_CID_FOCUS_RELATIVE with -3? current should reach 39, > >>>> V4L2_CID_FOCUS_ABSOLUTE is still at 42, the lens is still moving from > >>>> the application's point of view. > >>> > >>> Would there be a reason to implement both of these controls in a single > >>> driver? AFAIU, the relative one should be used if there absolute value > >>> isn't known to the driver. > >> > >> Probably not, but on the other hand there is nothing the prevents a > >> driver developer from doing so, right? Point is that should there be a > >> driver which does implement both controls, we are in trouble AFAIU. > > > > I think the documentation should be improved in this regard. > > The documentation of which control exactly? And what items should be added? Both V4L2_CID_FOCUS_ABSOLUTE and V4L2_CID_FOCUS_RELATIVE. For the former, the sentence "Positive values set the focus closer to the camera, negative values towards infinity." doesn't make much sense in the context. For the latter, what I mentioned earlier, i.e. this should be only implemented if the absolute value isn't known. It's not a driver's job to do simple arithmetics for the user space. In fact, it appears that no driver is using V4L2_CID_FOCUS_RELATIVE at the moment. So we could as well deprecate it (or remove from documentation altogether). -- Kind regards, Sakari Ailus
