linux-kernel - [PATCH 1/3] media: uvcvideo: Return the number of processed controls

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Message-Id: <20241210-uvc-data-backup-v1-1-77141e439cc3@chromium.org>
Date: Tue, 10 Dec 2024 22:22:22 +0000
From: Ricardo Ribalda <ribalda@...omium.org>
To: Laurent Pinchart <laurent.pinchart@...asonboard.com>, 
 Hans de Goede <hdegoede@...hat.com>, 
 Mauro Carvalho Chehab <mchehab@...nel.org>
Cc: linux-media@...r.kernel.org, linux-kernel@...r.kernel.org, 
 Ricardo Ribalda <ribalda@...omium.org>, stable@...nel.org
Subject: [PATCH 1/3] 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@...nel.org
Fixes: b4012002f3a3 ("[media] uvcvideo: Add support for control events")
Signed-off-by: Ricardo Ribalda <ribalda@...omium.org>
---
 drivers/media/usb/uvc/uvc_ctrl.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c
index 4fe26e82e3d1..7e2fc97c9f43 100644
--- a/drivers/media/usb/uvc/uvc_ctrl.c
+++ b/drivers/media/usb/uvc/uvc_ctrl.c
@@ -1810,9 +1810,14 @@ 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_entity *entity, int rollback, struct uvc_control **err_ctrl)
 {
+	unsigned int processed_ctrls = 0;
 	struct uvc_control *ctrl;
 	unsigned int i;
 	int ret;
@@ -1847,6 +1852,9 @@ 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),
@@ -1861,7 +1869,7 @@ 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,
@@ -1910,7 +1918,7 @@ int __uvc_ctrl_commit(struct uvc_fh *handle, int rollback,
 		uvc_ctrl_send_events(handle, ctrls->controls, ctrls->count);
 done:
 	mutex_unlock(&chain->ctrl_mutex);
-	return ret;
+	return ret < 0 ? ret : 0;
 }
 
 int uvc_ctrl_get(struct uvc_video_chain *chain,

-- 
2.47.0.338.g60cca15819-goog