2 files changed, 49 insertions, 8 deletions

diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c
index 44b6513c5264..f24272d483a2 100644
--- a/drivers/media/usb/uvc/uvc_ctrl.c
+++ b/drivers/media/usb/uvc/uvc_ctrl.c
@@ -1483,14 +1483,28 @@ static u32 uvc_get_ctrl_bitmap(struct uvc_control *ctrl,
 	return ~0;
 }
 
+/*
+ * Maximum retry count to avoid spurious errors with controls. Increasing this
+ * value does no seem to produce better results in the tested hardware.
+ */
+#define MAX_QUERY_RETRIES 2
+
 static int __uvc_queryctrl_boundaries(struct uvc_video_chain *chain,
 				      struct uvc_control *ctrl,
 				      struct uvc_control_mapping *mapping,
 				      struct v4l2_query_ext_ctrl *v4l2_ctrl)
 {
 	if (!ctrl->cached) {
-		int ret = uvc_ctrl_populate_cache(chain, ctrl);
-		if (ret < 0)
+		unsigned int retries;
+		int ret;
+
+		for (retries = 0; retries < MAX_QUERY_RETRIES; retries++) {
+			ret = uvc_ctrl_populate_cache(chain, ctrl);
+			if (ret != -EIO)
+				break;
+		}
+
+		if (ret)
 			return ret;
 	}
 
@@ -1567,6 +1581,7 @@ static int __uvc_query_v4l2_ctrl(struct uvc_video_chain *chain,
 {
 	struct uvc_control_mapping *master_map = NULL;
 	struct uvc_control *master_ctrl = NULL;
+	int ret;
 
 	memset(v4l2_ctrl, 0, sizeof(*v4l2_ctrl));
 	v4l2_ctrl->id = mapping->id;
@@ -1587,18 +1602,31 @@ static int __uvc_query_v4l2_ctrl(struct uvc_video_chain *chain,
 		__uvc_find_control(ctrl->entity, mapping->master_id,
 				   &master_map, &master_ctrl, 0, 0);
 	if (master_ctrl && (master_ctrl->info.flags & UVC_CTRL_FLAG_GET_CUR)) {
+		unsigned int retries;
 		s32 val;
 		int ret;
 
 		if (WARN_ON(uvc_ctrl_mapping_is_compound(master_map)))
 			return -EIO;
 
-		ret = __uvc_ctrl_get(chain, master_ctrl, master_map, &val);
-		if (ret < 0)
-			return ret;
+		for (retries = 0; retries < MAX_QUERY_RETRIES; retries++) {
+			ret = __uvc_ctrl_get(chain, master_ctrl, master_map,
+					     &val);
+			if (!ret)
+				break;
+			if (ret < 0 && ret != -EIO)
+				return ret;
+		}
 
-		if (val != mapping->master_manual)
-			v4l2_ctrl->flags |= V4L2_CTRL_FLAG_INACTIVE;
+		if (ret == -EIO) {
+			dev_warn_ratelimited(&chain->dev->udev->dev,
+					     "UVC non compliance: Error %d querying master control %x (%s)\n",
+					     ret, master_map->id,
+					     uvc_map_get_name(master_map));
+		} else {
+			if (val != mapping->master_manual)
+				v4l2_ctrl->flags |= V4L2_CTRL_FLAG_INACTIVE;
+		}
 	}
 
 	v4l2_ctrl->elem_size = uvc_mapping_v4l2_size(mapping);
@@ -1613,7 +1641,18 @@ static int __uvc_query_v4l2_ctrl(struct uvc_video_chain *chain,
 		return 0;
 	}
 
-	return __uvc_queryctrl_boundaries(chain, ctrl, mapping, v4l2_ctrl);
+	ret = __uvc_queryctrl_boundaries(chain, ctrl, mapping, v4l2_ctrl);
+	if (ret && !mapping->disabled) {
+		dev_warn(&chain->dev->udev->dev,
+			 "UVC non compliance: permanently disabling control %x (%s), due to error %d\n",
+			 mapping->id, uvc_map_get_name(mapping), ret);
+		mapping->disabled = true;
+	}
+
+	if (mapping->disabled)
+		v4l2_ctrl->flags |= V4L2_CTRL_FLAG_DISABLED;
+
+	return 0;
 }
 
 int uvc_query_v4l2_ctrl(struct uvc_video_chain *chain,
diff --git a/drivers/media/usb/uvc/uvcvideo.h b/drivers/media/usb/uvc/uvcvideo.h
index b9f8eb62ba1d..11d6e3c2ebdf 100644
--- a/drivers/media/usb/uvc/uvcvideo.h
+++ b/drivers/media/usb/uvc/uvcvideo.h
@@ -134,6 +134,8 @@ struct uvc_control_mapping {
 	s32 master_manual;
 	u32 slave_ids[2];
 
+	bool disabled;
+
 	const struct uvc_control_mapping *(*filter_mapping)
 				(struct uvc_video_chain *chain,
 				struct uvc_control *ctrl);