media: uvcvideo: Return the number of processed controls

If we let know our callers that we have not done anything, they will be
able to optimize their decisions.

Cc: stable@kernel.org
Fixes: b4012002f3a3 ("[media] uvcvideo: Add support for control events")
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
Message-ID: <20250224-uvc-data-backup-v2-1-de993ed9823b@chromium.org>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>

diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c
index e2052130f4c91333cdb88b9c4bbd4b15b8303fa3..0c4d84eab42a35b3a7e65b90fe40550901145b40 100644 (file)
--- a/drivers/media/usb/uvc/uvc_ctrl.c
+++ b/drivers/media/usb/uvc/uvc_ctrl.c
@@ -2101,12 +2101,17 @@ int uvc_ctrl_begin(struct uvc_video_chain *chain)
        return mutex_lock_interruptible(&chain->ctrl_mutex) ? -ERESTARTSYS : 0;
 }
 
+/*
+ * Returns the number of uvc controls that have been correctly set, or a
+ * negative number if there has been an error.
+ */
 static int uvc_ctrl_commit_entity(struct uvc_device *dev,
                                  struct uvc_fh *handle,
                                  struct uvc_entity *entity,
                                  int rollback,
                                  struct uvc_control **err_ctrl)
 {
+       unsigned int processed_ctrls = 0;
        struct uvc_control *ctrl;
        unsigned int i;
        int ret;
@@ -2141,6 +2146,9 @@ static int uvc_ctrl_commit_entity(struct uvc_device *dev,
                else
                        ret = 0;
 
+               if (!ret)
+                       processed_ctrls++;
+
                if (rollback || ret < 0)
                        memcpy(uvc_ctrl_data(ctrl, UVC_CTRL_DATA_CURRENT),
                               uvc_ctrl_data(ctrl, UVC_CTRL_DATA_BACKUP),
@@ -2159,7 +2167,7 @@ static int uvc_ctrl_commit_entity(struct uvc_device *dev,
                }
        }
 
-       return 0;
+       return processed_ctrls;
 }
 
 static int uvc_ctrl_find_ctrl_idx(struct uvc_entity *entity,
@@ -2206,6 +2214,7 @@ int __uvc_ctrl_commit(struct uvc_fh *handle, int rollback,
 
        if (!rollback)
                uvc_ctrl_send_events(handle, ctrls->controls, ctrls->count);
+       ret = 0;
 done:
        mutex_unlock(&chain->ctrl_mutex);
        return ret;