linux-kernel - Re: [PATCH v1] media: i2c: ov5640: Implement get_mbus

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Date:   Sat, 28 Jan 2023 11:06:11 +0100
From:   Jacopo Mondi <jacopo.mondi@...asonboard.com>
To:     Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc:     Jacopo Mondi <jacopo.mondi@...asonboard.com>,
        Marcel Ziswiler <marcel@...wiler.com>,
        linux-media@...r.kernel.org, kernel@...gutronix.de,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Francesco Dolcini <francesco.dolcini@...adex.com>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Aishwarya Kothari <aishwarya.kothari@...adex.com>,
        Marcel Ziswiler <marcel.ziswiler@...adex.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Steve Longerbeam <slongerbeam@...il.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1] media: i2c: ov5640: Implement get_mbus_config

Hi Laurent

On Fri, Jan 27, 2023 at 08:34:07PM +0200, Laurent Pinchart wrote:
> On Fri, Jan 27, 2023 at 06:50:03PM +0100, Jacopo Mondi wrote:
> > On Fri, Jan 27, 2023 at 04:12:44PM +0100, Marcel Ziswiler wrote:
> > > From: Aishwarya Kothari <aishwarya.kothari@...adex.com>
> > >
> > > Implement the introduced get_mbus_config operation to report the
> > > number of used data lanes on the MIPI CSI-2 interface.
> > >
> >
> > OV5640 can operate in parallel mode too.
> >
> > You can check how it currently configured with ov5640_is_csi2() and
> > populate struct v4l2_mbus_config accordingly.
>
> I'm also wondering which CSI-2 receiver needs .get_mbus_config() for the
> ov5640. The number of lanes is usually specified in DT, on both sides of
> the link. It's only when selecting a number of lanes dynamically at
> runtime that .get_mbus_config() is needed.
>

iirc Aishwarya and Marcel reported issues on i.MX6 so I presume they
need get_mbus_config as a drivers in staging/media/imx/ requires
that:

drivers/staging/media/imx/imx6-mipi-csi2.c
Fetches the remote mbus config to get the number of lanes and make
sure the bus type is CSI-2

drivers/staging/media/imx/imx-media-csi.c
Fetches the remote mbus config to deduce the bus type in use

In both cases I concur the callers can be fixed to parse their
endpoints but looking at commit 7318abface486d6a6389731810f5b60650daedb5
it seems that was not the plan (reason not clear to me)

> > > Signed-off-by: Aishwarya Kothari <aishwarya.kothari@...adex.com>
> > > Signed-off-by: Marcel Ziswiler <marcel.ziswiler@...adex.com>
> > >
> > > ---
> > >
> > >  drivers/media/i2c/ov5640.c | 14 ++++++++++++++
> > >  1 file changed, 14 insertions(+)
> > >
> > > diff --git a/drivers/media/i2c/ov5640.c b/drivers/media/i2c/ov5640.c
> > > index e0f908af581b..42d43f0d1e1c 100644
> > > --- a/drivers/media/i2c/ov5640.c
> > > +++ b/drivers/media/i2c/ov5640.c
> > > @@ -3733,6 +3733,19 @@ static int ov5640_init_cfg(struct v4l2_subdev *sd,
> > >  	return 0;
> > >  }
> > >
> > > +static int ov5640_get_mbus_config(struct v4l2_subdev *sd,
> > > +				   unsigned int pad,
> > > +				   struct v4l2_mbus_config *cfg)
> > > +{
> > > +	struct ov5640_dev *sensor = to_ov5640_dev(sd);
> > > +
> > > +	cfg->type = V4L2_MBUS_CSI2_DPHY;
> > > +	cfg->bus.mipi_csi2.num_data_lanes = sensor->ep.bus.mipi_csi2.num_data_lanes;
> > > +	cfg->bus.mipi_csi2.flags = 0;
> > > +
> > > +	return 0;
> > > +}
> > > +
> > >  static const struct v4l2_subdev_core_ops ov5640_core_ops = {
> > >  	.log_status = v4l2_ctrl_subdev_log_status,
> > >  	.subscribe_event = v4l2_ctrl_subdev_subscribe_event,
> > > @@ -3753,6 +3766,7 @@ static const struct v4l2_subdev_pad_ops ov5640_pad_ops = {
> > >  	.get_selection = ov5640_get_selection,
> > >  	.enum_frame_size = ov5640_enum_frame_size,
> > >  	.enum_frame_interval = ov5640_enum_frame_interval,
> > > +	.get_mbus_config = ov5640_get_mbus_config,
> > >  };
> > >
> > >  static const struct v4l2_subdev_ops ov5640_subdev_ops = {
>
> --
> Regards,
>
> Laurent Pinchart