media: uvcvideo: Add more logging to uvc_query_ctrl()

If we fail to query the control 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.

Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
Link: https://lore.kernel.org/r/20241128-uvc-readless-v5-2-cf16ed282af8@chromium.org
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c
index d2fe01bcd209e535b9cb47f41b6ed6aed7a100d6..a260e9868e8b6417e4324fbb3fc865a1f2f6f79d 100644 (file)
--- a/drivers/media/usb/uvc/uvc_video.c
+++ b/drivers/media/usb/uvc/uvc_video.c
@@ -117,8 +117,12 @@ int uvc_query_ctrl(struct uvc_device *dev, u8 query, u8 unit,
        error = *(u8 *)data;
        *(u8 *)data = tmp;
 
-       if (ret != 1)
+       if (ret != 1) {
+               dev_err_ratelimited(&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 < 0 ? ret : -EPIPE;
+       }
 
        uvc_dbg(dev, CONTROL, "Control error %u\n", error);