[PATCH 5.10.y 3/3] media: uvcvideo: Rollback non processed entities on error

[Ricardo Ribalda <ribalda@chromium.org>]

If we fail to commit an entity, we need to restore the
UVC_CTRL_DATA_BACKUP for the other uncommitted entities. Otherwise the
control cache and the device would be out of sync.

Cc: stable@kernel.org
Fixes: b4012002f3a3 ("[media] uvcvideo: Add support for control events")
Reported-by: Hans de Goede <hdegoede@redhat.com>
Closes: https://lore.kernel.org/linux-media/fe845e04-9fde-46ee-9763-a6f00867929a@redhat.com/
Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
Message-ID: <20250224-uvc-data-backup-v2-3-de993ed9823b@chromium.org>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
(cherry picked from commit a70705d3c020d0d5c3ab6a5cc93e011ac35e7d48)
Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
---
 drivers/media/usb/uvc/uvc_ctrl.c | 42 +++++++++++++++++++++-----------
 1 file changed, 28 insertions(+), 14 deletions(-)

diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c
index a4b082df3b06..4f67ba3a7c02 100644
--- a/drivers/media/usb/uvc/uvc_ctrl.c
+++ b/drivers/media/usb/uvc/uvc_ctrl.c
@@ -1577,7 +1577,7 @@ static int uvc_ctrl_commit_entity(struct uvc_device *dev,
 	unsigned int processed_ctrls = 0;
 	struct uvc_control *ctrl;
 	unsigned int i;
-	int ret;
+	int ret = 0;
 
 	if (entity == NULL)
 		return 0;
@@ -1605,8 +1605,6 @@ static int uvc_ctrl_commit_entity(struct uvc_device *dev,
 				dev->intfnum, ctrl->info.selector,
 				uvc_ctrl_data(ctrl, UVC_CTRL_DATA_CURRENT),
 				ctrl->info.size);
-		else
-			ret = 0;
 
 		if (!ret)
 			processed_ctrls++;
@@ -1618,14 +1616,22 @@ static int uvc_ctrl_commit_entity(struct uvc_device *dev,
 
 		ctrl->dirty = 0;
 
-		if (ret < 0)
-			return ret;
-
-		if (!rollback && handle &&
+		if (!rollback && handle && !ret &&
 		    ctrl->info.flags & UVC_CTRL_FLAG_ASYNCHRONOUS)
 			uvc_ctrl_set_handle(handle, ctrl, handle);
+
+		if (ret < 0 && !rollback) {
+			/*
+			 * If we fail to set a control, we need to rollback
+			 * the next ones.
+			 */
+			rollback = 1;
+		}
 	}
 
+	if (ret)
+		return ret;
+
 	return processed_ctrls;
 }
 
@@ -1635,23 +1641,31 @@ int __uvc_ctrl_commit(struct uvc_fh *handle, int rollback,
 {
 	struct uvc_video_chain *chain = handle->chain;
 	struct uvc_entity *entity;
-	int ret = 0;
+	int ret_out = 0;
+	int ret;
 
 	/* Find the control. */
 	list_for_each_entry(entity, &chain->entities, chain) {
 		ret = uvc_ctrl_commit_entity(chain->dev, handle, entity,
 					     rollback);
-		if (ret < 0)
-			goto done;
-		else if (ret > 0 && !rollback)
+		if (ret < 0) {
+			/*
+			 * When we fail to commit an entity, we need to
+			 * restore the UVC_CTRL_DATA_BACKUP for all the
+			 * controls in the other entities, otherwise our cache
+			 * and the hardware will be out of sync.
+			 */
+			rollback = 1;
+
+			ret_out = ret;
+		} else if (ret > 0 && !rollback) {
 			uvc_ctrl_send_events(handle, entity, xctrls,
 					     xctrls_count);
+		}
 	}
 
-	ret = 0;
-done:
 	mutex_unlock(&chain->ctrl_mutex);
-	return ret;
+	return ret_out;
 }
 
 int uvc_ctrl_get(struct uvc_video_chain *chain,
-- 
2.50.0.727.gbf7dc18ff4-goog