linux-kernel - Re: [PATCH 1/4] media: subdev: Add checks for subdev features

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Date: Thu, 4 Apr 2024 11:09:58 +0000
From: Sakari Ailus <sakari.ailus@...ux.intel.com>
To: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
Cc: Mauro Carvalho Chehab <mchehab@...nel.org>,
	Hans Verkuil <hverkuil@...all.nl>,
	Laurent Pinchart <laurent.pinchart@...asonboard.com>,
	Umang Jain <umang.jain@...asonboard.com>,
	linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/4] media: subdev: Add checks for subdev features

Moi,

On Thu, Apr 04, 2024 at 01:50:00PM +0300, Tomi Valkeinen wrote:
> Add some checks to verify that the subdev driver implements required
> features.
> 
> A subdevice that supports streams (V4L2_SUBDEV_FL_STREAMS) must do one
> of the following:
> 
> - Implement neither .enable/disable_streams() nor .s_stream(), if the
>   subdev is part of a video driver that uses an internal method to
>   enable the subdev.
> - Implement only .enable/disable_streams(), if support for legacy
>   sink-side subdevices is not needed.
> - Implement .enable/disable_streams() and .s_stream(), if support for
>   legacy sink-side subdevices is needed.
> 
> At the moment the framework doesn't check this requirement. Add the
> check.
> 
> Signed-off-by: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
> ---
>  drivers/media/v4l2-core/v4l2-subdev.c | 27 +++++++++++++++++++++++++++
>  1 file changed, 27 insertions(+)
> 
> diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c
> index 4c6198c48dd6..b90b5185e87f 100644
> --- a/drivers/media/v4l2-core/v4l2-subdev.c
> +++ b/drivers/media/v4l2-core/v4l2-subdev.c
> @@ -1519,6 +1519,33 @@ int __v4l2_subdev_init_finalize(struct v4l2_subdev *sd, const char *name,
>  				struct lock_class_key *key)
>  {
>  	struct v4l2_subdev_state *state;
> +	struct device *dev = sd->dev;
> +	bool has_disable_streams;
> +	bool has_enable_streams;
> +	bool has_s_stream;
> +
> +	/* Check that the subdevice implements the required features */
> +
> +	has_s_stream = sd->ops && sd->ops->video && sd->ops->video->s_stream;
> +	has_enable_streams = sd->ops && sd->ops->pad && sd->ops->pad->enable_streams;
> +	has_disable_streams = sd->ops && sd->ops->pad && sd->ops->pad->disable_streams;

There is v4l2_subdev_has_op(). Please also run:

	./scripts/checkpatch.pl --strict --max-line-length=80

on this.

> +
> +	if (has_enable_streams != has_disable_streams) {
> +		dev_err(dev,
> +			"subdev '%s' must implement both or neither of .enable_streams() and .disable_streams()\n",
> +			sd->name);
> +		return -EINVAL;
> +	}
> +
> +	if (sd->flags & V4L2_SUBDEV_FL_STREAMS) {
> +		if (has_s_stream && !has_enable_streams) {

Is the s_stream callback allowed to be something else than NULL or
v4l2_subdev_s_stream_helper?

> +			dev_err(dev,
> +				"subdev '%s' must implement .enable/disable_streams()\n",
> +				sd->name);
> +
> +			return -EINVAL;
> +		}
> +	}
>  
>  	state = __v4l2_subdev_state_alloc(sd, name, key);
>  	if (IS_ERR(state))
> 

-- 
Terveisin,

Sakari Ailus