Hi Sakari On Wed, 12 Apr 2023 at 15:39, Sakari Ailus <sakari.ailus@xxxxxxxxxxxxxxx> wrote: > > 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). Atomisp and ov5693 are using it, but only to manipulate the value behind V4L2_CID_FOCUS_ABSOLUTE. I don't know why elixir.bootlin.com isn't picking up those references. https://github.com/torvalds/linux/blob/master/drivers/staging/media/atomisp/pci/atomisp_ioctl.c#L1766 https://github.com/torvalds/linux/blob/master/drivers/staging/media/atomisp/i2c/ov5693/atomisp-ov5693.c#L966 Dave
