[PATCH v2 2/2] media: uvcvideo: Add more logging to uvc_query_ctrl()

[Ricardo Ribalda <ribalda@chromium.org>]

If we fail to query the ctrl error code there is no information on dmesg
or in uvc_dbg. This makes difficult to debug the issue.

Print a proper error message when we cannot retrieve the error code from
the device.

Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
---
 drivers/media/usb/uvc/uvc_video.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c
index f125b3ba50f2..6efbfa609059 100644
--- a/drivers/media/usb/uvc/uvc_video.c
+++ b/drivers/media/usb/uvc/uvc_video.c
@@ -111,8 +111,12 @@ int uvc_query_ctrl(struct uvc_device *dev, u8 query, u8 unit,
 	error = *(u8 *)data;
 	*(u8 *)data = tmp;
 
-	if (ret != 1)
-		return ret < 0 ? ret : -EPIPE;
+	if (ret != 1) {
+		dev_err(&dev->udev->dev,
+			"Failed to query (%s) UVC error code control %u on unit %u: %d (exp. 1).\n",
+			uvc_query_name(query), cs, unit, ret);
+		return ret ? ret : -EPIPE;
+	}
 
 	uvc_dbg(dev, CONTROL, "Control error %u\n", error);
 

-- 
2.47.0.rc0.187.ge670bccf7e-goog