Re: [PATCH v4 25/29] media: v4l2-subdev: Move subdev client capabilities into a new struct

[Jacopo Mondi <jacopo.mondi@ideasonboard.com>]

Hi Sakari

On Wed, Apr 08, 2026 at 06:39:34PM +0300, Sakari Ailus wrote:
> Add struct v4l2_subdev_client_info to hold sub-device client capability
> bits that used to be stored in the client_caps field of struct
> v4l2_subdev_fh. The intent is to enable passing this struct to sub-device
> pad operation callbacks for capability information. The main reason why
> this is a new struct instead of a u64 field is that modifying the callback
> arguments requires touching almost every sub-device driver and that is
> desirable to avoid in the future, should more than the client capability bits
> need to be known to the callbacks.
>
> Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
> Reviewed-by: Mirela Rabulea <mirela.rabulea@nxp.com>
> ---
>  drivers/media/v4l2-core/v4l2-subdev.c |  8 ++++----
>  include/media/v4l2-subdev.h           | 12 ++++++++++--
>  2 files changed, 14 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c
> index 40b28e070726..eaa408832c6b 100644
> --- a/drivers/media/v4l2-core/v4l2-subdev.c
> +++ b/drivers/media/v4l2-core/v4l2-subdev.c
> @@ -612,7 +612,7 @@ subdev_ioctl_get_state(struct v4l2_subdev *sd, struct v4l2_subdev_fh *subdev_fh,
>  	case VIDIOC_SUBDEV_S_FRAME_INTERVAL: {
>  		struct v4l2_subdev_frame_interval *fi = arg;
>
> -		if (!(subdev_fh->client_caps &
> +		if (!(subdev_fh->ci.client_caps &
>  		      V4L2_SUBDEV_CLIENT_CAP_INTERVAL_USES_WHICH))
>  			fi->which = V4L2_SUBDEV_FORMAT_ACTIVE;
>
> @@ -652,7 +652,7 @@ static long subdev_do_ioctl(struct file *file, unsigned int cmd, void *arg,
>  	struct v4l2_subdev_fh *subdev_fh = to_v4l2_subdev_fh(vfh);
>  	bool ro_subdev = test_bit(V4L2_FL_SUBDEV_RO_DEVNODE, &vdev->flags);
>  	bool streams_subdev = sd->flags & V4L2_SUBDEV_FL_STREAMS;
> -	bool client_supports_streams = subdev_fh->client_caps &
> +	bool client_supports_streams = subdev_fh->ci.client_caps &
>  				       V4L2_SUBDEV_CLIENT_CAP_STREAMS;
>  	int rval;
>
> @@ -1119,7 +1119,7 @@ static long subdev_do_ioctl(struct file *file, unsigned int cmd, void *arg,
>  	case VIDIOC_SUBDEV_G_CLIENT_CAP: {
>  		struct v4l2_subdev_client_capability *client_cap = arg;
>
> -		client_cap->capabilities = subdev_fh->client_caps;
> +		client_cap->capabilities = subdev_fh->ci.client_caps;
>
>  		return 0;
>  	}
> @@ -1139,7 +1139,7 @@ static long subdev_do_ioctl(struct file *file, unsigned int cmd, void *arg,
>  		client_cap->capabilities &= (V4L2_SUBDEV_CLIENT_CAP_STREAMS |
>  					     V4L2_SUBDEV_CLIENT_CAP_INTERVAL_USES_WHICH);
>
> -		subdev_fh->client_caps = client_cap->capabilities;
> +		subdev_fh->ci.client_caps = client_cap->capabilities;


I'm sorry for being annoying, but the discussion on v2 ended with the
question on why we can't propagate the client caps to the drivers
using the subdev state.

I understand we have the active state which is stored in the subdev
and not per-file handle. But ioctls are called on a file handle and it
seems trivial to me copy the caps from the subdev_fh to the active
state.

It would result in a much smaller set of changes.

What am I missing ?


>
>  		return 0;
>  	}
> diff --git a/include/media/v4l2-subdev.h b/include/media/v4l2-subdev.h
> index 93b672edd08e..e0861acc638d 100644
> --- a/include/media/v4l2-subdev.h
> +++ b/include/media/v4l2-subdev.h
> @@ -734,6 +734,14 @@ struct v4l2_subdev_state {
>  	struct v4l2_subdev_stream_configs stream_configs;
>  };
>
> +/**
> + * struct v4l2_subdev_client_info - Sub-device client information
> + * @client_caps: bitmask of ``V4L2_SUBDEV_CLIENT_CAP_*``
> + */
> +struct v4l2_subdev_client_info {
> +	u64 client_caps;
> +};
> +
>  /**
>   * struct v4l2_subdev_pad_ops - v4l2-subdev pad level operations
>   *
> @@ -1129,14 +1137,14 @@ struct v4l2_subdev {
>   * @vfh: pointer to &struct v4l2_fh
>   * @state: pointer to &struct v4l2_subdev_state
>   * @owner: module pointer to the owner of this file handle
> - * @client_caps: bitmask of ``V4L2_SUBDEV_CLIENT_CAP_*``
> + * @ci: sub-device client info related to this file handle
>   */
>  struct v4l2_subdev_fh {
>  	struct v4l2_fh vfh;
>  	struct module *owner;
>  #if defined(CONFIG_VIDEO_V4L2_SUBDEV_API)
>  	struct v4l2_subdev_state *state;
> -	u64 client_caps;
> +	struct v4l2_subdev_client_info ci;
>  #endif
>  };
>
> --
> 2.47.3
>
>