Re: [PATCH v11 40/66] media: Document enable_streams and disable_streams behaviour

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

Hi Sakari,

Thank you for the patch.

On Mon, Aug 25, 2025 at 12:50:41PM +0300, Sakari Ailus wrote:
> Document that enable_streams may start additional streams and
> disable_streams may not disable requested streams if other related streams
> are still enabled.
> 
> Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
> ---
>  include/media/v4l2-subdev.h | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/include/media/v4l2-subdev.h b/include/media/v4l2-subdev.h
> index 4b28086808c9..96a9c869ffb1 100644
> --- a/include/media/v4l2-subdev.h
> +++ b/include/media/v4l2-subdev.h
> @@ -814,6 +814,10 @@ struct v4l2_subdev_state {
>   *	V4L2_SUBDEV_CAP_STREAMS sub-device capability flag can ignore the mask
>   *	argument.
>   *
> + *	Starting the requested streams may require starting additional
> + *	streams. Streams that are started together due to hardware are called a
> + *	stream group.

I initially interpreted this as meaning that, to start the requested
streams at the hardware level, the caller may need to start additional
streams. That is, the .enable_streams() call may not have any effect
until other streams are also started by the caller.

> + *
>   * @disable_streams: Disable the streams defined in streams_mask on the given
>   *	source pad. Subdevs that implement this operation must use the active
>   *	state management provided by the subdev core (enabled through a call to
> @@ -823,6 +827,9 @@ struct v4l2_subdev_state {
>   *	Drivers that support only a single stream without setting the
>   *	V4L2_SUBDEV_CAP_STREAMS sub-device capability flag can ignore the mask
>   *	argument.
> + *
> + *	A stream is only disabled once all streams in the stream group are
> + *	disabled.

But this implies it's the other way around. A clarification is needed.
Which behaviour are you trying to document ?

>   */
>  struct v4l2_subdev_pad_ops {
>  	int (*enum_mbus_code)(struct v4l2_subdev *sd,

-- 
Regards,

Laurent Pinchart