linux-kernel - Re: [PATCH 1/2] media: v4l2-async: Pass pointer to struct v4l2_subdev in match

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Date:   Sun, 15 Mar 2020 12:56:34 +0200
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Lad Prabhakar <prabhakar.csengg@...il.com>
Cc:     Niklas <niklas.soderlund@...natech.se>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Hans Verkuil <hverkuil-cisco@...all.nl>,
        linux-media@...r.kernel.org, linux-renesas-soc@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
Subject: Re: [PATCH 1/2] media: v4l2-async: Pass pointer to struct
 v4l2_subdev in match_custom callback

Hi Prabhakar,

Thank you for the patch.

On Sun, Mar 15, 2020 at 10:27:23AM +0000, Lad Prabhakar wrote:
> Passing a pointer to struct device for the match_custom callback is of no
> use as in the bridge driver to match the fwnode, so instead pass the
> struct v4l2_subdev pointer so that the bridge driver has enough
> information to match against the subdevices.

I'm not sure I like this. Conceptually speaking, the driver that
registers the notifier wants to get v4l2_subdev instances corresponding
to devices. A struct device is thus all it should need. Giving the match
function access to the subdev opens the door to all kind of nasty hacks.

In any case, I don't think is is required, see my reply to patch 2/2.

> Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
> ---
>  drivers/media/v4l2-core/v4l2-async.c | 2 +-
>  include/media/v4l2-async.h           | 4 ++--
>  2 files changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/media/v4l2-core/v4l2-async.c b/drivers/media/v4l2-core/v4l2-async.c
> index 8bde33c21ce4..f897d4025f97 100644
> --- a/drivers/media/v4l2-core/v4l2-async.c
> +++ b/drivers/media/v4l2-core/v4l2-async.c
> @@ -80,7 +80,7 @@ static bool match_custom(struct v4l2_subdev *sd, struct v4l2_async_subdev *asd)
>  		/* Match always */
>  		return true;
>  
> -	return asd->match.custom.match(sd->dev, asd);
> +	return asd->match.custom.match(sd, asd);
>  }
>  
>  static LIST_HEAD(subdev_list);
> diff --git a/include/media/v4l2-async.h b/include/media/v4l2-async.h
> index 8319284c93cb..8c014e3bbd6c 100644
> --- a/include/media/v4l2-async.h
> +++ b/include/media/v4l2-async.h
> @@ -86,8 +86,8 @@ struct v4l2_async_subdev {
>  			unsigned short address;
>  		} i2c;
>  		struct {
> -			bool (*match)(struct device *dev,
> -				      struct v4l2_async_subdev *sd);
> +			bool (*match)(struct v4l2_subdev *sd,
> +				      struct v4l2_async_subdev *asd);
>  			void *priv;
>  		} custom;
>  	} match;

-- 
Regards,

Laurent Pinchart