[libcamera-devel] [PATCH 20/25] media: ov5647: Program mode only if it has changed

[Jacopo Mondi]

Hi Dafna,

On Tue, Jun 30, 2020 at 11:32:12AM +0200, Dafna Hirschfeld wrote:
>
>
> On 30.06.20 09:43, Jacopo Mondi wrote:
> > Hi Dafna,
> >
> > On Mon, Jun 29, 2020 at 07:48:16PM +0200, Dafna Hirschfeld wrote:
> > >
> > >
> > > On 23.06.20 18:55, Jacopo Mondi wrote:
> > > > Store in the driver structure a pointer to the currently applied mode
> > > > and program a new one at s_stream(1) time only if it has changed.
> > >
> > > Hi,
> > > I think this can be more readably implemented with a 'is_streaming' boolean
> > > field.
> >
> > How would you like to use an 'is_streaming' flag to decide if the
> > sensor mode has to be updated ?
>
> since 'current_mode' is set to NULL upon `ov5647_stream_off`
> and you return from 'ov5647_set_stream' immediately if 'mode == current_mode'
> it seem very similar to returning immediately from 'ov5647_set_stream' if the
> device is currently streaming.

No, the code returns immediately from ov5647_set_mode() if mode ==
current_mode. The modes comparison makes sure the sensor is not
reprogrammed if the mode hasn't changed. The remaning part of
s_stream() is executed regardless of the mode configuration. Am I
missing some part of the picture ?

>
> But actually in this patch it seems to be possible to change the mode
> while streaming, if the callbacks are executed:
>
> s_stream(1)
> s_fmt
> s_stream(1)
>
> which is maybe a bug?

The new format is stored in sensor->mode, and applied at the next
s_stream(1) operation if it differs from the already programmed one,
at least, this is how it is intended to work, have you found any
failing s_stream/set_fmt/s_stream which could be caused by a bug ?

Thanks
  j
>
> Thanks,
> Dafna
>
> >
> > Thanks
> >     j
> >
> >
> > >
> > > Thanks,
> > > Dafna
> > >
> > > >
> > > > Signed-off-by: Jacopo Mondi <jacopo at jmondi.org>
> > > > ---
> > > >    drivers/media/i2c/ov5647.c | 16 +++++++++++++++-
> > > >    1 file changed, 15 insertions(+), 1 deletion(-)
> > > >
> > > > diff --git a/drivers/media/i2c/ov5647.c b/drivers/media/i2c/ov5647.c
> > > > index 39e320f321bd8..ac114269e1c73 100644
> > > > --- a/drivers/media/i2c/ov5647.c
> > > > +++ b/drivers/media/i2c/ov5647.c
> > > > @@ -96,6 +96,7 @@ struct ov5647 {
> > > >    	bool				clock_ncont;
> > > >    	struct v4l2_ctrl_handler	ctrls;
> > > >    	struct ov5647_mode		*mode;
> > > > +	struct ov5647_mode		*current_mode;
> > > >    };
> > > >    static inline struct ov5647 *to_sensor(struct v4l2_subdev *sd)
> > > > @@ -750,9 +751,13 @@ static int ov5647_set_virtual_channel(struct v4l2_subdev *sd, int channel)
> > > >    static int ov5647_set_mode(struct v4l2_subdev *sd)
> > > >    {
> > > >    	struct i2c_client *client = v4l2_get_subdevdata(sd);
> > > > +	struct ov5647 *sensor = to_sensor(sd);
> > > >    	u8 resetval, rdval;
> > > >    	int ret;
> > > > +	if (sensor->mode == sensor->current_mode)
> > > > +		return 0;
> > > > +
> > > >    	ret = ov5647_read(sd, OV5647_SW_STANDBY, &rdval);
> > > >    	if (ret < 0)
> > > >    		return ret;
> > > > @@ -778,6 +783,8 @@ static int ov5647_set_mode(struct v4l2_subdev *sd)
> > > >    			return ret;
> > > >    	}
> > > > +	sensor->current_mode = sensor->mode;
> > > > +
> > > >    	return 0;
> > > >    }
> > > > @@ -816,6 +823,7 @@ static int ov5647_stream_on(struct v4l2_subdev *sd)
> > > >    static int ov5647_stream_off(struct v4l2_subdev *sd)
> > > >    {
> > > > +	struct ov5647 *sensor = to_sensor(sd);
> > > >    	int ret;
> > > >    	ret = ov5647_write(sd, OV5647_REG_MIPI_CTRL00, MIPI_CTRL00_CLOCK_LANE_GATE |
> > > > @@ -827,7 +835,13 @@ static int ov5647_stream_off(struct v4l2_subdev *sd)
> > > >    	if (ret < 0)
> > > >    		return ret;
> > > > -	return ov5647_write(sd, OV5640_REG_PAD_OUT, 0x01);
> > > > +	ret = ov5647_write(sd, OV5640_REG_PAD_OUT, 0x01);
> > > > +	if (ret < 0)
> > > > +		return ret;
> > > > +
> > > > +	sensor->current_mode = NULL;
> > > > +
> > > > +	return 0;
> > > >    }
> > > >    static int set_sw_standby(struct v4l2_subdev *sd, bool standby)
> > > >