Re: [PATCH v2 4/5] media: ov5640: fix auto controls values when switching to manual mode

Laurent Pinchart
2018-09-10T15:39:25Z

Hi Hugues,

On Monday, 10 September 2018 13:23:41 EEST Hugues FRUCHET wrote:
> On 09/06/2018 03:31 PM, Laurent Pinchart wrote:
> > On Monday, 13 August 2018 13:19:45 EEST Hugues Fruchet wrote:
> >
> >> When switching from auto to manual mode, V4L2 core is calling
> >> g_volatile_ctrl() in manual mode in order to get the manual initial
> >> value. Remove the manual mode check/return to not break this behaviour.
> >>
> >> Signed-off-by: Hugues Fruchet <hugues.fruchet@st.com>
> >> ---
> >> drivers/media/i2c/ov5640.c | 4 ----
> >> 1 file changed, 4 deletions(-)
> >>
> >> diff --git a/drivers/media/i2c/ov5640.c b/drivers/media/i2c/ov5640.c
> >> index 9fb17b5..c110a6a 100644
> >> --- a/drivers/media/i2c/ov5640.c
> >> +++ b/drivers/media/i2c/ov5640.c
> >> @@ -2277,16 +2277,12 @@ static int ov5640_g_volatile_ctrl(struct
> >> v4l2_ctrl *ctrl)
> >>
> >> switch (ctrl->id) {
> >> case V4L2_CID_AUTOGAIN:
> >> - if (!ctrl->val)
> >> - return 0;
> >>
> >> val = ov5640_get_gain(sensor);
> >> if (val < 0)
> >> return val;
> >>
> >> sensor->ctrls.gain->val = val;
> >> break;
> >
> > What is this even supposed to do ? Only the V4L2_CID_GAIN and
> > V4L2_CID_EXPOSURE have the volatile flag set. Why can't this code be
> > replaced with
>
> This is because V4L2_CID_AUTOGAIN & V4L2_CID_GAIN are declared as
> auto-cluster:
> static int ov5640_init_controls(struct ov5640_dev *sensor)
> /* Auto/manual gain */
> ctrls->auto_gain = v4l2_ctrl_new_std(hdl, ops, V4L2_CID_AUTOGAIN,
> 0, 1, 1, 1);
> ctrls->gain = v4l2_ctrl_new_std(hdl, ops, V4L2_CID_GAIN,
> 0, 1023, 1, 0);
> [...]
> v4l2_ctrl_auto_cluster(2, &ctrls->auto_gain, 0, true);
>
> By checking many other drivers that are using clustered auto controls,
> they are all doing that way:
>
> ctrls->auto_x = v4l2_ctrl_new_std(CID_X_AUTO..
> ctrls->x = v4l2_ctrl_new_std(CID_X..
> v4l2_ctrl_auto_cluster(2, &ctrls->auto, 0, true);
>
> g_volatile_ctrl(ctrl)
> switch (ctrl->id) {
> case CID_X_AUTO:
> ctrls->x->val = READ_REG()

Seems like cargo-cult to me. Why is this better than the construct below ?

> > case V4L2_CID_GAIN:
> > val = ov5640_get_gain(sensor);
> > if (val < 0)
> > return val;
> > ctrl->val = val;
> > break;
> >
> >> case V4L2_CID_EXPOSURE_AUTO:
> >> - if (ctrl->val == V4L2_EXPOSURE_MANUAL)
> >> - return 0;
> >> val = ov5640_get_exposure(sensor);
> >> if (val < 0)
> >> return val;
> >
> > And same here.

--
Regards,

Laurent Pinchart