Re: [PATCH v3 3/9] media: subdev: Add checks for subdev features

[Umang Jain]

Hi Tomi,

On 10/04/24 6:05 pm, 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@xxxxxxxxxxxxxxxx>

The code looks aligned with the restrictions mentioned in the commit 
message.

Only one question in case 3), does the .s_stream() needs to be helper 
function I think, can we (or do we) need to check that as well?

Reviewed-by: Umang Jain <umang.jain@xxxxxxxxxxxxxxxx>

> ---
>   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 4a531c2b16c4..606a909cd778 100644
> --- a/drivers/media/v4l2-core/v4l2-subdev.c
> +++ b/drivers/media/v4l2-core/v4l2-subdev.c
> @@ -1533,6 +1533,33 @@ 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 = v4l2_subdev_has_op(sd, video, s_stream);
> +	has_enable_streams = v4l2_subdev_has_op(sd, pad, enable_streams);
> +	has_disable_streams = v4l2_subdev_has_op(sd, pad, disable_streams);
> +
> +	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) {
> +			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))