Hi Michael, On Tue, Jun 06, 2023 at 03:15:33PM +0200, Michael Riesch wrote: > On 6/6/23 12:36, Laurent Pinchart wrote: > > On Tue, Apr 25, 2023 at 11:45:12AM +0200, Michael Riesch wrote: > >> The control V4L2_CID_FOCUS_RELATIVE only makes sense if the device cannot > >> handle absolute focal point positioning with V4L2_CID_FOCUS_ABSOLUTE. > >> Clarify this in the documentation. > >> > >> Signed-off-by: Michael Riesch <michael.riesch@xxxxxxxxxxxxxx> > >> --- > >> Documentation/userspace-api/media/v4l/ext-ctrls-camera.rst | 4 +++- > >> 1 file changed, 3 insertions(+), 1 deletion(-) > >> > >> diff --git a/Documentation/userspace-api/media/v4l/ext-ctrls-camera.rst b/Documentation/userspace-api/media/v4l/ext-ctrls-camera.rst > >> index df29150dce7b..42cf4c3cda0c 100644 > >> --- a/Documentation/userspace-api/media/v4l/ext-ctrls-camera.rst > >> +++ b/Documentation/userspace-api/media/v4l/ext-ctrls-camera.rst > >> @@ -147,7 +147,9 @@ enum v4l2_exposure_metering - > >> This control moves the focal point of the camera by the specified > >> amount. The unit is undefined. Positive values move the focus closer > >> to the camera, negative values towards infinity. This is a > >> - write-only control. > >> + write-only control. It should be implemented only if the device cannot > >> + handle absolute values. > >> + > > > > Extra blank line. > > Will fix that. > > > I don't think this is right. The control was added for the UVC driver, > > and there are devices that implement both absolute and relative focus. > > I am by no means an expert here and just following Sakari's suggestion > here (see [0]). I can drop the patch, leave it as-is, or modify it. > Whatever makes sense to you guys. But maybe I should leave this to > someone more knowledgeable in this area and drop the patch from my > series. The changes above are completely orthogonal to my work. V4L2_CID_FOCUS_RELATIVE is an annoying control. It was introduced for UVC, and to my surprise, it turns out it has never been implemented in the uvcvideo driver. The 3 devices I know of that implement the UVC relative focus control also implement the UVC absolute focus control. I'm tempted to deprecate this control completely. Sakari, any opinion ? > >> > >> ``V4L2_CID_FOCUS_AUTO (boolean)`` > >> Enables continuous automatic focus adjustments. The effect of manual > >> > > > > [0] https://lore.kernel.org/all/ZDbChgZJHVaaX3%2Fx@kekkonen.localdomain/ -- Regards, Laurent Pinchart
