Hi Jacopo Thanks for the patch. On Mon, 7 Nov 2022 at 20:50, Jacopo Mondi <jacopo@xxxxxxxxxx> wrote: > > When a new image format is applied on the sensor it is necessary to > update the vertical and horizontal blanking limits, to comply with the > new visibile sizes. > > Add that part to the documentation of camera sensor subdevices. > > Signed-off-by: Jacopo Mondi <jacopo@xxxxxxxxxx> > --- > .../driver-api/media/camera-sensor.rst | 29 +++++++++++++++++++ > 1 file changed, 29 insertions(+) > > diff --git a/Documentation/driver-api/media/camera-sensor.rst b/Documentation/driver-api/media/camera-sensor.rst > index bb7d62db4cd1..31f74f85ebc5 100644 > --- a/Documentation/driver-api/media/camera-sensor.rst > +++ b/Documentation/driver-api/media/camera-sensor.rst > @@ -107,6 +107,35 @@ The first entity in the linear pipeline is the pixel array. The pixel array may > be followed by other entities that are there to allow configuring binning, > skipping, scaling or digital crop :ref:`v4l2-subdev-selections`. > > +Blankings initialization and reconfiguration > +"""""""""""""""""""""""""""""""""""""""""""" > + > +The value used to initialize the vertical and horizontal blanking controls > +should be selected in order to realize, in association with the driver default > +format and default pixel rate, a reasonable frame rate output, usually one of > +the standard 15, 30 or 60 frame per second. > + > +When a new frame size is applied on the subdevice sensor drivers are requested s/requested/required. There's no option about it - if the ranges change then the limits must be updated. > +to update the limits of their blankings controls. > + > +The V4L2 control framework provides the ``v4l2_ctrl_modify_range()`` function > +(and the unlocked ``__v4l2_ctrl_modify_range()`` counterpart) to assist drivers > +in re-computing the controls limits. > + > +The new maximum limit for the controls should be re-calculated using the > +newly applied visibile width and height s/visibile/visible However that depends on whether patch 1 is correct or not. > + > +.. code-block:: c > + > + max_vblank = MAX_VTS - sensor->fmt.height; > + ret = __v4l2_ctrl_modify_range(sensor->ctrls.vblank, > + sensor->ctrls.vblank->minimum, > + max_vblank, sensor->ctrls.vblank->step, > + sensor->ctrls.vblank->minimum); > + > +The blankings default value is reset to the control minimum and the V4L2 > +control framework automatically clamps the control's value in the new limits. So this raises the question we debated previously - what should the default signify, and does it need to change? Dave > + > USB cameras etc. devices > ~~~~~~~~~~~~~~~~~~~~~~~~ > > -- > 2.38.1 >
