On 16/03/2021 19:00, Ricardo Ribalda wrote:
> If a control is inactive return -EACCES to let the userspace know that
> the value will not be applied automatically when the control is active
> again.
>
> Signed-off-by: Ricardo Ribalda <riba...@chromium.org>
> Suggested-by: Hans Verkuil <hverk...@xs4all.nl>
> ---
> drivers/media/usb/uvc/uvc_ctrl.c | 17 ++++++++++++++++-
> 1 file changed, 16 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/media/usb/uvc/uvc_ctrl.c
> b/drivers/media/usb/uvc/uvc_ctrl.c
> index ba14733db757..98614e1be829 100644
> --- a/drivers/media/usb/uvc/uvc_ctrl.c
> +++ b/drivers/media/usb/uvc/uvc_ctrl.c
> @@ -1578,6 +1578,18 @@ int uvc_ctrl_begin(struct uvc_video_chain *chain)
> return mutex_lock_interruptible(&chain->ctrl_mutex) ? -ERESTARTSYS : 0;
> }
>
> +static bool uvc_ctrl_is_inactive(struct uvc_control *ctrl)
This doesn't test if the control is inactive, it tests if it *might* be
inactive. To test if it is really inactive would require checking the value
of the master control.
> +{
> + struct uvc_control_mapping *map;
> +
> + list_for_each_entry(map, &ctrl->info.mappings, list) {
> + if (map->master_id)
> + return true;
> + }
> +
> + return false;
> +}
> +
> static int uvc_ctrl_commit_entity(struct uvc_device *dev,
> struct uvc_entity *entity, int rollback)
> {
> @@ -1621,8 +1633,11 @@ static int uvc_ctrl_commit_entity(struct uvc_device
> *dev,
>
> ctrl->dirty = 0;
>
> - if (ret < 0)
> + if (ret < 0) {
> + if (uvc_ctrl_is_inactive(ctrl))
> + return -EACCES;
So here you assume that if setting the control failed, and if the control
might be inactive, then it probably was inactive.
I feel a bit uncomfortable by this assumption.
Regards,
Hans
> return ret;
> + }
> }
>
> return 0;
>
