| Message ID | 20221107204959.37691-4-jacopo@jmondi.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Documentation: media: camera_sensor: Document blankings handling | expand |
Hi Jacopo On Mon, 7 Nov 2022 at 20:50, Jacopo Mondi <jacopo@jmondi.org> wrote: > > The maximum achieable exposure time in a camera sensor is usually s/achieable/achievable > bound by the total frame height (visible + blankings) minus a fixed > sensor-speific offset. s/speific/specific visible, or analogue crop? > When the vertical blanking control value is changed, the exposure > control limits should be updated as well. > > Add this to the camera sensor documentation. > > Signed-off-by: Jacopo Mondi <jacopo@jmondi.org> > --- > .../driver-api/media/camera-sensor.rst | 33 +++++++++++++++++++ > 1 file changed, 33 insertions(+) > > diff --git a/Documentation/driver-api/media/camera-sensor.rst b/Documentation/driver-api/media/camera-sensor.rst > index 31f74f85ebc5..76206c7647d6 100644 > --- a/Documentation/driver-api/media/camera-sensor.rst > +++ b/Documentation/driver-api/media/camera-sensor.rst > @@ -179,3 +179,36 @@ used to obtain device's power state after the power state transition: > The function returns a non-zero value if it succeeded getting the power count or > runtime PM was disabled, in either of which cases the driver may proceed to > access the device. > + > +Resetting exposure on vertical blanking update Resetting exposure limits on vertical blanking update You don't want to update the value (unless it is now outside the permissible range). > +"""""""""""""""""""""""""""""""""""""""""""""" > + > +The sensor exposure time, specified by the ``V4L2_CID_EXPOSURE`` control, is > +usually limited by a maximum value which is equal to maximum vertical blankings > +minus a known offset usually specified in the chip programming manual. limited to a maximum value related to the frame interval. Frequently it is a number of lines less than the frame length that will be specified in the sensor documentation. > +When a new ``V4L2_CID_VBLANK`` value is applied, regardless of it being actually > +programmed to the hardware or not, the limits of the ``V4L2_CID_EXPOSURE`` > +control should be updated as well. > + > +The typical coding pattern that realizes that in the ``.s_ctrl`` callback > +handler is: > + > +.. code-block:: c > + #define SENSOR_EXPOSURE_OFFSET <see sensor documentation> > + static int s_ctrl(struct v4l2_ctrl *ctrl) > + { > + int exp_max; > + > + switch (ctrl->id) { > + case V4L2_CID_VBLANK: > + exp_max = sensor->fmt.height + ctrl->val - 4; sensor->fmt.height + ctrl->val - SENSOR_EXPOSURE_OFFSET. Discussion on patch 1 over the use of sensor->fmt.height. Dave > + __v4l2_ctrl_modify_range(sensor->ctrls.exposure, > + sensor->ctrls.exposure->minimum, > + exp_max, sensor->ctrls.exposure->step, > + sensor->ctrls.exposure->default_value); > + break; > + } > + > + if (!pm_runtime_get_if_in_use(&sensor->i2c_client->dev)) > + return 0; > -- > 2.38.1 >
diff --git a/Documentation/driver-api/media/camera-sensor.rst b/Documentation/driver-api/media/camera-sensor.rst index 31f74f85ebc5..76206c7647d6 100644 --- a/Documentation/driver-api/media/camera-sensor.rst +++ b/Documentation/driver-api/media/camera-sensor.rst @@ -179,3 +179,36 @@ used to obtain device's power state after the power state transition: The function returns a non-zero value if it succeeded getting the power count or runtime PM was disabled, in either of which cases the driver may proceed to access the device. + +Resetting exposure on vertical blanking update +"""""""""""""""""""""""""""""""""""""""""""""" + +The sensor exposure time, specified by the ``V4L2_CID_EXPOSURE`` control, is +usually limited by a maximum value which is equal to maximum vertical blankings +minus a known offset usually specified in the chip programming manual. + +When a new ``V4L2_CID_VBLANK`` value is applied, regardless of it being actually +programmed to the hardware or not, the limits of the ``V4L2_CID_EXPOSURE`` +control should be updated as well. + +The typical coding pattern that realizes that in the ``.s_ctrl`` callback +handler is: + +.. code-block:: c + + static int s_ctrl(struct v4l2_ctrl *ctrl) + { + int exp_max; + + switch (ctrl->id) { + case V4L2_CID_VBLANK: + exp_max = sensor->fmt.height + ctrl->val - 4; + __v4l2_ctrl_modify_range(sensor->ctrls.exposure, + sensor->ctrls.exposure->minimum, + exp_max, sensor->ctrls.exposure->step, + sensor->ctrls.exposure->default_value); + break; + } + + if (!pm_runtime_get_if_in_use(&sensor->i2c_client->dev)) + return 0;
The maximum achieable exposure time in a camera sensor is usually bound by the total frame height (visible + blankings) minus a fixed sensor-speific offset. When the vertical blanking control value is changed, the exposure control limits should be updated as well. Add this to the camera sensor documentation. Signed-off-by: Jacopo Mondi <jacopo@jmondi.org> --- .../driver-api/media/camera-sensor.rst | 33 +++++++++++++++++++ 1 file changed, 33 insertions(+)