linux-kernel - [PATCH v4 2/2] media: uvcvideo: Add more logging to uvc_query

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Message-Id: <20241120-uvc-readless-v4-2-4672dbef3d46@chromium.org>
Date: Wed, 20 Nov 2024 15:26:20 +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>, 
 Sakari Ailus <sakari.ailus@...ux.intel.com>
Subject: [PATCH v4 2/2] media: uvcvideo: Add more logging to
 uvc_query_ctrl()

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.

Reviewed-by: Hans de Goede <hdegoede@...hat.com>
Signed-off-by: Ricardo Ribalda <ribalda@...omium.org>
---
 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 482c4ceceaac..00d9e3420fb6 100644
--- a/drivers/media/usb/uvc/uvc_video.c
+++ b/drivers/media/usb/uvc/uvc_video.c
@@ -112,8 +112,12 @@ 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);
 

-- 
2.47.0.338.g60cca15819-goog