Re: [PATCH v3 4/7] media: i2c: imx290: Introduce initial "off" mode & link freq

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

On Mon, Sep 02, 2024 at 10:55:04PM +0200, Benjamin Bara wrote:
> On Mon, 2 Sept 2024 at 21:58, Laurent Pinchart wrote:
> > On Mon, Sep 02, 2024 at 05:57:29PM +0200, bbara93@gmail.com wrote:
> > > From: Benjamin Bara <benjamin.bara@skidata.com>
> > >
> > > To be compliant to the V4L2 API, the driver currently "randomly" decides
> > > on one of the two supported modes which also implies a link frequency.
> > >
> > > Add a new mode and frequency which symbolize that the sensor is not in
> > > use. This can be used as a default value during probe() and enables us
> > > to avoid communication with the sensor.
> >
> > I really doin't like this change. I would like to instead move away from
> > modes and make the driver freely configurable.
> 
> Which controls do you want to have freely configurable? At least on the
> imx290 the exposure limits depend on the blanking, and the blanking
> limits depend on the format. As the format is defined by the mode on
> imx290, I think this will be quite hard with the current controls.

I want to make the format freely configurable.

> > Furthermore, the concept of an initial unconfigured state isn't valid
> > in V4L2. The driver must fully initialize the whole device state at
> > probe time.
> 
> I understand that and it makes sense to me. But given the dependencies
> from above and the fact that the format is currently part of this
> "state", it makes the "freely configurable" intention even harder :-(

Why can't we simply initialize the controls with limits that correspond
to the default format ? I don't understand what issue this is trying to
solve.

> > > Signed-off-by: Benjamin Bara <benjamin.bara@skidata.com>
> > > ---
> > > Changes since v2:
> > > - new
> > > ---
> > >  drivers/media/i2c/imx290.c | 29 +++++++++++++++++++++++------
> > >  1 file changed, 23 insertions(+), 6 deletions(-)
> > >
> > > diff --git a/drivers/media/i2c/imx290.c b/drivers/media/i2c/imx290.c
> > > index 6812e7cb9e23..ece4d66001f5 100644
> > > --- a/drivers/media/i2c/imx290.c
> > > +++ b/drivers/media/i2c/imx290.c
> > > @@ -425,14 +425,17 @@ static const struct imx290_csi_cfg imx290_csi_297mhz = {
> > >  /* supported link frequencies */
> > >  #define FREQ_INDEX_1080P     0
> > >  #define FREQ_INDEX_720P              1
> > > +#define FREQ_INDEX_OFF               2
> > >  static const s64 imx290_link_freq_2lanes[] = {
> > >       [FREQ_INDEX_1080P] = 445500000,
> > >       [FREQ_INDEX_720P] = 297000000,
> > > +     [FREQ_INDEX_OFF] = 0,
> > >  };
> > >
> > >  static const s64 imx290_link_freq_4lanes[] = {
> > >       [FREQ_INDEX_1080P] = 222750000,
> > >       [FREQ_INDEX_720P] = 148500000,
> > > +     [FREQ_INDEX_OFF] = 0,
> > >  };
> > >
> > >  /*
> > > @@ -552,6 +555,10 @@ static const struct imx290_mode imx290_modes_4lanes[] = {
> > >       },
> > >  };
> > >
> > > +static const struct imx290_mode imx290_mode_off = {
> > > +     .link_freq_index = FREQ_INDEX_OFF,
> > > +};
> > > +
> > >  static inline const struct imx290_mode *imx290_modes_ptr(const struct imx290 *imx290)
> > >  {
> > >       if (imx290->nlanes == 2)
> > > @@ -876,10 +883,19 @@ static unsigned int imx290_get_blank_min(const struct imx290 *imx290, bool v)
> > >  static void imx290_ctrl_update(struct imx290 *imx290,
> > >                              const struct imx290_mode *mode)
> > >  {
> > > -     unsigned int hblank_min = mode->hmax_min - mode->width;
> > > -     unsigned int hblank_max = IMX290_HMAX_MAX - mode->width;
> > > -     unsigned int vblank_min = mode->vmax_min - mode->height;
> > > -     unsigned int vblank_max = IMX290_VMAX_MAX - mode->height;
> > > +     unsigned int hblank_min, hblank_max, vblank_min, vblank_max;
> > > +
> > > +     if (mode == &imx290_mode_off) {
> > > +             hblank_min = imx290_get_blank_min(imx290, false);
> > > +             hblank_max = HBLANK_MAX;
> > > +             vblank_min = imx290_get_blank_min(imx290, true);
> > > +             vblank_max = VBLANK_MAX;
> > > +     } else {
> > > +             hblank_min = mode->hmax_min - mode->width;
> > > +             hblank_max = IMX290_HMAX_MAX - mode->width;
> > > +             vblank_min = mode->vmax_min - mode->height;
> > > +             vblank_max = IMX290_VMAX_MAX - mode->height;
> > > +     }
> > >
> > >       __v4l2_ctrl_s_ctrl(imx290->link_freq, mode->link_freq_index);
> > >
> > > @@ -932,7 +948,8 @@ static int imx290_ctrl_init(struct imx290 *imx290)
> > >       imx290->link_freq =
> > >               v4l2_ctrl_new_int_menu(&imx290->ctrls, &imx290_ctrl_ops,
> > >                                      V4L2_CID_LINK_FREQ,
> > > -                                    imx290_link_freqs_num(imx290) - 1, 0,
> > > +                                    imx290_link_freqs_num(imx290) - 1,
> > > +                                    FREQ_INDEX_OFF,
> > >                                      imx290_link_freqs_ptr(imx290));
> > >       if (imx290->link_freq)
> > >               imx290->link_freq->flags |= V4L2_CTRL_FLAG_READ_ONLY;
> > > @@ -1278,7 +1295,7 @@ static int imx290_subdev_init(struct imx290 *imx290)
> > >       struct v4l2_subdev_state *state;
> > >       int ret;
> > >
> > > -     imx290->current_mode = &imx290_modes_ptr(imx290)[0];
> > > +     imx290->current_mode = &imx290_mode_off;
> > >
> > >       v4l2_i2c_subdev_init(&imx290->sd, client, &imx290_subdev_ops);
> > >       imx290->sd.internal_ops = &imx290_internal_ops;
> > >

-- 
Regards,

Laurent Pinchart