Re: [PATCH v7 2/7] media: uvcvideo: add uvc_ctrl_get_fixed for getting default value

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

Hi Yunke,

Thank you for the patch.

On Tue, Jun 28, 2022 at 04:57:00PM +0900, Yunke Cao wrote:
> Introduce a new uvc_ctrl_get_fixed. It simply calls query_v4l2_ctrl()

"fixed" sounds a bit confusing to me. How about calling it
uvc_ctrl_get_boundary() or uvc_ctrl_get_limit() ? A better name could
possibly be found as the default value isn't a limit.
uvc_ctrl_get_info() comes to mind, but it wouldn't match the UVC
GET_INFO concept, which may be confusing.

> for now, but is easier to extend to support compound controls and
> V4L2_CTRL_WHICH_MIN/MAX_VAL in the following patches.
> 
> Reviewed-by: Ricardo Ribalda <ribalda@chromium.org>
> Signed-off-by: Yunke Cao <yunkec@google.com>
> ---
>  drivers/media/usb/uvc/uvc_ctrl.c | 13 +++++++++++++
>  drivers/media/usb/uvc/uvc_v4l2.c |  6 +-----
>  drivers/media/usb/uvc/uvcvideo.h |  2 ++
>  3 files changed, 16 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c
> index 0e78233fc8a0..772d9d28a520 100644
> --- a/drivers/media/usb/uvc/uvc_ctrl.c
> +++ b/drivers/media/usb/uvc/uvc_ctrl.c
> @@ -1697,6 +1697,19 @@ int uvc_ctrl_get(struct uvc_video_chain *chain,
>  	return __uvc_ctrl_get(chain, ctrl, mapping, &xctrl->value);
>  }
>  
> +int uvc_ctrl_get_fixed(struct uvc_video_chain *chain,
> +		       struct v4l2_ext_control *xctrl)
> +{
> +	struct v4l2_queryctrl qc = { .id = xctrl->id };
> +	int ret = uvc_query_v4l2_ctrl(chain, &qc);
> +
> +	if (ret < 0)
> +		return ret;
> +
> +	xctrl->value = qc.default_value;
> +	return 0;
> +}
> +
>  int uvc_ctrl_set(struct uvc_fh *handle,
>  	struct v4l2_ext_control *xctrl)
>  {
> diff --git a/drivers/media/usb/uvc/uvc_v4l2.c b/drivers/media/usb/uvc/uvc_v4l2.c
> index 648dcd579e81..0366d05895a9 100644
> --- a/drivers/media/usb/uvc/uvc_v4l2.c
> +++ b/drivers/media/usb/uvc/uvc_v4l2.c
> @@ -1042,15 +1042,11 @@ static int uvc_ioctl_g_ext_ctrls(struct file *file, void *fh,
>  
>  	if (ctrls->which == V4L2_CTRL_WHICH_DEF_VAL) {
>  		for (i = 0; i < ctrls->count; ++ctrl, ++i) {
> -			struct v4l2_queryctrl qc = { .id = ctrl->id };
> -
> -			ret = uvc_query_v4l2_ctrl(chain, &qc);
> +			ret = uvc_ctrl_get_fixed(chain, ctrl);
>  			if (ret < 0) {
>  				ctrls->error_idx = i;
>  				return ret;
>  			}
> -
> -			ctrl->value = qc.default_value;
>  		}
>  
>  		return 0;
> diff --git a/drivers/media/usb/uvc/uvcvideo.h b/drivers/media/usb/uvc/uvcvideo.h
> index c5b4febd2d94..ba028ba7c34e 100644
> --- a/drivers/media/usb/uvc/uvcvideo.h
> +++ b/drivers/media/usb/uvc/uvcvideo.h
> @@ -901,6 +901,8 @@ static inline int uvc_ctrl_rollback(struct uvc_fh *handle)
>  }
>  
>  int uvc_ctrl_get(struct uvc_video_chain *chain, struct v4l2_ext_control *xctrl);
> +int uvc_ctrl_get_fixed(struct uvc_video_chain *chain,
> +		       struct v4l2_ext_control *xctrl);
>  int uvc_ctrl_set(struct uvc_fh *handle, struct v4l2_ext_control *xctrl);
>  int uvc_ctrl_is_accessible(struct uvc_video_chain *chain, u32 v4l2_id,
>  			   bool read);

-- 
Regards,

Laurent Pinchart