[media.git/next] media: uvcvideo: Add more logging to uvc_query_ctrl()

[media-ci]

On Thu Nov 28 20:53:42 2024 +0000, Ricardo Ribalda wrote:
> 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 <hdego...@redhat.com>
> Signed-off-by: Ricardo Ribalda <riba...@chromium.org>
> Link: 
> https://lore.kernel.org/r/20241128-uvc-readless-v5-2-cf16ed282...@chromium.org
> Signed-off-by: Hans de Goede <hdego...@redhat.com>
> Reviewed-by: Laurent Pinchart <laurent.pinch...@ideasonboard.com>
> Signed-off-by: Laurent Pinchart <laurent.pinch...@ideasonboard.com>
> Signed-off-by: Mauro Carvalho Chehab <mchehab+hua...@kernel.org>

Patch committed.

Thanks,
Mauro Carvalho Chehab

 drivers/media/usb/uvc/uvc_video.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

---

diff --git a/drivers/media/usb/uvc/uvc_video.c 
b/drivers/media/usb/uvc/uvc_video.c
index d2fe01bcd209..a260e9868e8b 100644
--- 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);