Re: [V9, 2/2] media: i2c: ov02a10: Add OV02A10 image sensor driver

[Tomasz Figa <tfiga@chromium.org>]

On Thu, Jun 11, 2020 at 11:53 AM Sakari Ailus
<sakari.ailus@linux.intel.com> wrote:
>
> Hi Tomasz,
>
> On Wed, Jun 10, 2020 at 07:44:55PM +0000, Tomasz Figa wrote:
> > Hi Dongchun,
> >
> > On Sat, May 23, 2020 at 04:41:03PM +0800, Dongchun Zhu wrote:
> > > Add a V4L2 sub-device driver for OV02A10 image sensor.
> > >
> > > Signed-off-by: Dongchun Zhu <dongchun.zhu@mediatek.com>
> > > ---
> > >  MAINTAINERS                 |    1 +
> > >  drivers/media/i2c/Kconfig   |   13 +
> > >  drivers/media/i2c/Makefile  |    1 +
> > >  drivers/media/i2c/ov02a10.c | 1025 +++++++++++++++++++++++++++++++++++++++++++
> > >  4 files changed, 1040 insertions(+)
> > >  create mode 100644 drivers/media/i2c/ov02a10.c
> > >
> >
> > Thank you for the patch. Please see my comments inline.
> >
> > [snip]
> > > diff --git a/drivers/media/i2c/ov02a10.c b/drivers/media/i2c/ov02a10.c
> > > new file mode 100644
> > > index 0000000..160a0b5
> > > --- /dev/null
> > > +++ b/drivers/media/i2c/ov02a10.c
> > [snip]
> > > +static const char * const ov02a10_test_pattern_menu[] = {
> > > +   "Disabled",
> > > +   "Color Bar",
> >
> > nit: We should normalize this to one of the standard names. What is the
> > pattern on this sensor? Is it perhaps "Eight Vertical Colour Bars"?
> >
> > > +};
> > [snip]
> > > +static int ov02a10_set_fmt(struct v4l2_subdev *sd,
> > > +                      struct v4l2_subdev_pad_config *cfg,
> > > +                      struct v4l2_subdev_format *fmt)
> > > +{
> > > +   struct ov02a10 *ov02a10 = to_ov02a10(sd);
> > > +   struct v4l2_mbus_framefmt *mbus_fmt = &fmt->format;
> > > +
> > > +   mutex_lock(&ov02a10->mutex);
> > > +
> >
> >
> > Don't we need to handle the case when fmt->which is V4L2_SUBDEV_FORMAT_TRY,
> > which is used for trying the format, but not applying it to the hardware?
>
> Yes.
>
> >
> > > +   if (ov02a10->streaming) {
> > > +           mutex_unlock(&ov02a10->mutex);
> > > +           return -EBUSY;
> > > +   }
> > > +
> > > +   /* Only one sensor mode supported */
> > > +   mbus_fmt->code = ov02a10->fmt.code;
> > > +   ov02a10_fill_fmt(ov02a10->cur_mode, mbus_fmt);
> > > +   ov02a10->fmt = fmt->format;
> > > +
> > > +   mutex_unlock(&ov02a10->mutex);
> > > +
> > > +   return 0;
> > > +}
> > > +
> > > +static int ov02a10_get_fmt(struct v4l2_subdev *sd,
> > > +                      struct v4l2_subdev_pad_config *cfg,
> > > +                      struct v4l2_subdev_format *fmt)
> > > +{
> > > +   struct ov02a10 *ov02a10 = to_ov02a10(sd);
> > > +   struct v4l2_mbus_framefmt *mbus_fmt = &fmt->format;
> > > +
> > > +   mutex_lock(&ov02a10->mutex);
> > > +
> > > +   fmt->format = ov02a10->fmt;
> >
> > Ditto.
> >
> > > +   mbus_fmt->code = ov02a10->fmt.code;
> > > +   ov02a10_fill_fmt(ov02a10->cur_mode, mbus_fmt);
> > > +
> > > +   mutex_unlock(&ov02a10->mutex);
> > > +
> > > +   return 0;
> > > +}
> > > +
> > > +static int ov02a10_enum_mbus_code(struct v4l2_subdev *sd,
> > > +                             struct v4l2_subdev_pad_config *cfg,
> > > +                             struct v4l2_subdev_mbus_code_enum *code)
> > > +{
> > > +   struct ov02a10 *ov02a10 = to_ov02a10(sd);
> > > +
> > > +   if (code->index >= ARRAY_SIZE(supported_modes))
> > > +           return -EINVAL;
> >
> > Hmm, supported_modes[] doesn't seem to hold the information about mbus
> > codes. Should this just perhaps be "!= 0"?
> >
> > > +
> > > +   code->code = ov02a10->fmt.code;
> > > +
> > > +   return 0;
> > > +}
> > [snip]
> > > +static int ov02a10_entity_init_cfg(struct v4l2_subdev *sd,
> > > +                              struct v4l2_subdev_pad_config *cfg)
> > > +{
> > > +   struct v4l2_subdev_format fmt = {
> > > +           .which = cfg ? V4L2_SUBDEV_FORMAT_TRY : V4L2_SUBDEV_FORMAT_ACTIVE,
> > > +           .format = {
> > > +                   .width = 1600,
> > > +                   .height = 1200,
> > > +           }
> > > +   };
> > > +
> > > +   ov02a10_set_fmt(sd, cfg, &fmt);
> > > +
> > > +   return 0;
> > > +}
> > > +
> >
> > I'm not familiar with this init_cfg operation and the documentation is very
> > sparse about it. Sakari, is this a correct implementation?
>
> The purpose is to initialise a pad configuration (format and selection
> rectangles) to the device defaults. As there seem to be no selection
> rectangles, this seems fine to me.

Thanks. I traced the code and could only see one place where the
callback is being called and that was with cfg != NULL. Still, the
code above uses "cfg ?" as a check to determine whether TRY or ACTIVE
should be passed to which. Is that also correct?

Best regards,
Tomasz