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Date:   Fri, 4 Sep 2020 09:55:53 +0200
From:   Jacopo Mondi <jacopo@jmondi.org>
To:     Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc:     Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>,
        Mauro Carvalho Chehab <mchehab@kernel.org>,
        Sakari Ailus <sakari.ailus@iki.fi>,
        Hans Verkuil <hverkuil@xs4all.nl>, linux-media@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-renesas-soc@vger.kernel.org,
        Biju Das <biju.das.jz@bp.renesas.com>,
        Prabhakar <prabhakar.csengg@gmail.com>
Subject: Re: [PATCH v3 1/2] media: i2c: ov772x: Add support for BT656 mode
Message-ID: <20200904075553.qjdyskcpext7fxcy@uno.localdomain>
References: <20200824190406.27478-1-prabhakar.mahadev-lad.rj@bp.renesas.com>
 <20200824190406.27478-2-prabhakar.mahadev-lad.rj@bp.renesas.com>
 <20200904012000.GA9369@pendragon.ideasonboard.com>
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Hi Laurent,

On Fri, Sep 04, 2020 at 04:20:00AM +0300, Laurent Pinchart wrote:
> Hi Prabhakar,
>
> Thank you for the patch.
>
> On Mon, Aug 24, 2020 at 08:04:05PM +0100, Lad Prabhakar wrote:
> > Add support to read the bus-type and enable BT656 mode if needed.
> >
> > Also fail probe if unsupported bus_type is detected.
> >
> > Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
> > Reviewed-by: Biju Das <biju.das.jz@bp.renesas.com>
> > ---
> >  drivers/media/i2c/ov772x.c | 32 ++++++++++++++++++++++++++++++++
> >  1 file changed, 32 insertions(+)
> >
> > diff --git a/drivers/media/i2c/ov772x.c b/drivers/media/i2c/ov772x.c
> > index 2cc6a678069a..67764d647526 100644
> > --- a/drivers/media/i2c/ov772x.c
> > +++ b/drivers/media/i2c/ov772x.c
> > @@ -31,6 +31,7 @@
> >  #include <media/v4l2-ctrls.h>
> >  #include <media/v4l2-device.h>
> >  #include <media/v4l2-event.h>
> > +#include <media/v4l2-fwnode.h>
> >  #include <media/v4l2-image-sizes.h>
> >  #include <media/v4l2-subdev.h>
> >
> > @@ -434,6 +435,7 @@ struct ov772x_priv {
> >  #ifdef CONFIG_MEDIA_CONTROLLER
> >  	struct media_pad pad;
> >  #endif
> > +	struct v4l2_fwnode_endpoint ep;
> >  };
> >
> >  /*
> > @@ -581,6 +583,13 @@ static int ov772x_s_stream(struct v4l2_subdev *sd, int enable)
> >  	if (priv->streaming == enable)
> >  		goto done;
> >
> > +	if (priv->ep.bus_type == V4L2_MBUS_BT656) {
> > +		ret = regmap_update_bits(priv->regmap, COM7, ITU656_ON_OFF,
> > +					 enable ? ITU656_ON_OFF : ~ITU656_ON_OFF);
> > +		if (ret)
> > +			goto done;
> > +	}
> > +
> >  	ret = regmap_update_bits(priv->regmap, COM2, SOFT_SLEEP_MODE,
> >  				 enable ? 0 : SOFT_SLEEP_MODE);
> >  	if (ret)
> > @@ -1354,6 +1363,7 @@ static const struct v4l2_subdev_ops ov772x_subdev_ops = {
> >
> >  static int ov772x_probe(struct i2c_client *client)
> >  {
> > +	struct fwnode_handle *endpoint;
> >  	struct ov772x_priv	*priv;
> >  	int			ret;
> >  	static const struct regmap_config ov772x_regmap_config = {
> > @@ -1415,6 +1425,28 @@ static int ov772x_probe(struct i2c_client *client)
> >  		goto error_clk_put;
> >  	}
> >
> > +	endpoint = fwnode_graph_get_next_endpoint(dev_fwnode(&client->dev),
> > +						  NULL);
> > +	if (!endpoint) {
> > +		dev_err(&client->dev, "endpoint node not found\n");
> > +		ret = -EINVAL;
> > +		goto error_clk_put;
> > +	}
> > +
> > +	ret = v4l2_fwnode_endpoint_parse(endpoint, &priv->ep);
>
> v4l2_fwnode_endpoint_parse() is deprecated for new drivers,
> v4l2_fwnode_endpoint_alloc_parse() is recommended instead. Please note
> that v4l2_fwnode_endpoint_free() then needs to be called in the error
> path and in remove().

Doesn't alloc_parse() differ from just _parse() as it reserve space
for the 'link-frequencies' array ? As this device does not support
CSI-2 and the 'link-frequencies' property is not allows in bindings,
isn't using endpoint_parse() better as it saves a call to _free() ?

Or are we deprecating that function unconditionally ? The
documentation suggests "please use v4l2_fwnode_endpoint_alloc_parse()
in new drivers" but here it doesn't seem required..

>
> On the other hand, not setting .bus_type and letting the parse()
> function determine the but type automatically is also deprecated, and I
> don't think forcing drivers to call v4l2_fwnode_endpoint_alloc_parse()
> once for each bus type until one succeeds is a good API. As change will
> be needed in that API, you can ignore v4l2_fwnode_endpoint_alloc_parse()
> for the time being if you want.

But indeed relying on auto-guessing of the bus type is deprecated since
some time now (and the API could be improved, yes). Sorry I missed
that yesterday.

As we support parallel and bt.656 only I must be honest I don't mind
it here as otherwise the code would be more complex for no real gain,
but I defer this to Sakari which has been fighting the battle against
auto-guessing since a long time now  :)


>
> Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
>
> > +	fwnode_handle_put(endpoint);
> > +	if (ret) {
> > +		dev_err(&client->dev, "Could not parse endpoint\n");
> > +		goto error_clk_put;
> > +	}
> > +
> > +	if (priv->ep.bus_type != V4L2_MBUS_PARALLEL &&
> > +	    priv->ep.bus_type != V4L2_MBUS_BT656) {
> > +		dev_err(&client->dev, "Unsupported bus type %d\n",
> > +			priv->ep.bus_type);
> > +		goto error_clk_put;
> > +	}
> > +
> >  	ret = ov772x_video_probe(priv);
> >  	if (ret < 0)
> >  		goto error_gpio_put;
>
> --
> Regards,
>
> Laurent Pinchart