Re: [PATCH v2 1/1] media: v4l2-subdev: Fail {enable,disable}_streams and s_streaming nicely

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

On Mon, Mar 23, 2026 at 12:56:55PM +0200, Sakari Ailus wrote:
> If a sub-device does not set enable_streams() and disable_streams() pad
> ops while it sets the s_stream() video op to
> v4l2_subdev_s_stream_helper(), enabling or disabling streaming either way
> on the sub-device will result calling v4l2_subdev_s_stream_helper() and
> v4l2_subdev_{enable,disable}_streams() recursively, exhausting the stack.
> Return -ENOIOCTLCMD in this case to handle the situation gracefully.

This is not a valid use case, right ? Can we WARN() ?

> Reported-by: David Heidelberg <david@ixit.cz>
> Fixes: b62949ddaa52 ("media: subdev: Support single-stream case in v4l2_subdev_enable/disable_streams()")
> Cc: stable@vger.kernel.org
> Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
> ---
> since v1:
> 
> - Better patch description.
> 
>  drivers/media/v4l2-core/v4l2-subdev.c | 16 ++++++++++------
>  1 file changed, 10 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c
> index 831c69c958b8..f8ea4afc6cbb 100644
> --- a/drivers/media/v4l2-core/v4l2-subdev.c
> +++ b/drivers/media/v4l2-core/v4l2-subdev.c
> @@ -2334,11 +2334,13 @@ int v4l2_subdev_enable_streams(struct v4l2_subdev *sd, u32 pad,
>  
>  	/* Fallback on .s_stream() if .enable_streams() isn't available. */
>  	use_s_stream = !v4l2_subdev_has_op(sd, pad, enable_streams);
> -
> -	if (!use_s_stream)
> +	if (!use_s_stream) {
>  		state = v4l2_subdev_lock_and_get_active_state(sd);
> -	else
> +	} else {
> +		if (!v4l2_subdev_has_op(sd, video, s_stream))
> +			return -ENOIOCTLCMD;
>  		state = NULL;
> +	}
>  
>  	/*
>  	 * Verify that the requested streams exist and that they are not
> @@ -2435,11 +2437,13 @@ int v4l2_subdev_disable_streams(struct v4l2_subdev *sd, u32 pad,
>  
>  	/* Fallback on .s_stream() if .disable_streams() isn't available. */
>  	use_s_stream = !v4l2_subdev_has_op(sd, pad, disable_streams);
> -
> -	if (!use_s_stream)
> +	if (!use_s_stream) {
>  		state = v4l2_subdev_lock_and_get_active_state(sd);
> -	else
> +	} else {
> +		if (!v4l2_subdev_has_op(sd, video, s_stream))
> +			return -ENOIOCTLCMD;
>  		state = NULL;
> +	}
>  
>  	/*
>  	 * Verify that the requested streams exist and that they are not

-- 
Regards,

Laurent Pinchart