linux-kernel - Re: [PATCH v2] v4l2-subdev: Return -EOPNOTSUPP for unsupported pad type in call_get_frame

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Message-ID: <20241007181654.GD14766@pendragon.ideasonboard.com>
Date: Mon, 7 Oct 2024 21:16:54 +0300
From: Laurent Pinchart <laurent.pinchart@...asonboard.com>
To: Prabhakar <prabhakar.csengg@...il.com>
Cc: Sakari Ailus <sakari.ailus@...ux.intel.com>,
	Mauro Carvalho Chehab <mchehab@...nel.org>,
	Hans Verkuil <hverkuil-cisco@...all.nl>,
	linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-renesas-soc@...r.kernel.org,
	Biju Das <biju.das.jz@...renesas.com>,
	Fabrizio Castro <fabrizio.castro.jz@...esas.com>,
	Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
Subject: Re: [PATCH v2] v4l2-subdev: Return -EOPNOTSUPP for unsupported pad
 type in call_get_frame_desc()

Hi Prabhakar,

Thank you for the patch.

On Mon, Oct 07, 2024 at 01:38:09PM +0100, Prabhakar wrote:
> From: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
> 
> The `get_frame_desc()` operation should always be called on a source pad,
> which is indicated by the `MEDIA_PAD_FL_SOURCE` flag. This patch adds a
> check in `call_get_frame_desc()` to ensure that the `MEDIA_PAD_FL_SOURCE`
> flag is set for the pad before invoking `get_frame_desc()`. If the pad is
> not a source pad, the function will return an `-EOPNOTSUPP` error,
> signaling that the operation is not supported on non-source pads.
> 
> Suggested-by: Sakari Ailus <sakari.ailus@...ux.intel.com>
> Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
> ---
> v1->v2
> - Added a check for CONFIG_MEDIA_CONTROLLER, as the `entity` member in 
>   `struct v4l2_subdev` is only available when CONFIG_MEDIA_CONTROLLER
>   is enabled.
> ---
>  drivers/media/v4l2-core/v4l2-subdev.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c
> index de9ac67574bb..446fbc3805c7 100644
> --- a/drivers/media/v4l2-core/v4l2-subdev.c
> +++ b/drivers/media/v4l2-core/v4l2-subdev.c
> @@ -325,6 +325,11 @@ static int call_get_frame_desc(struct v4l2_subdev *sd, unsigned int pad,
>  	unsigned int i;
>  	int ret;
>  
> +#if defined(CONFIG_MEDIA_CONTROLLER)
> +	if (!(sd->entity.pads[pad].flags & MEDIA_PAD_FL_SOURCE))

As this should really not happen, I wonder if we shouldn't be more
vocal:

	if (WARN_ON(!(sd->entity.pads[pad].flags & MEDIA_PAD_FL_SOURCE)))

Sakari, what do you think ? Either way,

Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@...asonboard.com>

> +		return -EOPNOTSUPP;
> +#endif
> +
>  	memset(fd, 0, sizeof(*fd));
>  
>  	ret = sd->ops->pad->get_frame_desc(sd, pad, fd);

-- 
Regards,

Laurent Pinchart