Some cameras, like the ELMO MX-P3, do not return all the bytes
requested from a control if it can fit in less bytes.
Eg: Returning 0xab instead of 0x00ab.
usb 3-9: Failed to query (GET_DEF) UVC control 3 on unit 2: 1 (exp. 2).
Extend the returned value from the camera and return it.
Cc: stable@xxxxxxxxxxxxxxx
Fixes: a763b9fb58be ("media: uvcvideo: Do not return positive errors in uvc_query_ctrl()")
Reviewed-by: Hans de Goede <hdegoede@xxxxxxxxxx>
Signed-off-by: Ricardo Ribalda <ribalda@xxxxxxxxxxxx>
---
drivers/media/usb/uvc/uvc_video.c | 16 ++++++++++++++++
1 file changed, 16 insertions(+)
diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c
index cd9c29532fb0..482c4ceceaac 100644
--- a/drivers/media/usb/uvc/uvc_video.c
+++ b/drivers/media/usb/uvc/uvc_video.c
@@ -79,6 +79,22 @@ int uvc_query_ctrl(struct uvc_device *dev, u8 query, u8 unit,
if (likely(ret == size))
return 0;
+ /*
+ * In UVC the data is usually represented in little-endian.
+ * Some devices return shorter USB control packets that expected if the
+ * returned value can fit in less bytes. Zero all the bytes that the
+ * device have not written.
+ * We exclude UVC_GET_INFO from the quirk. UVC_GET_LEN does not need to
+ * be excluded because its size is always 1.
+ */
+ if (ret > 0 && query != UVC_GET_INFO) {
+ memset(data + ret, 0, size - ret);
+ dev_warn_once(&dev->udev->dev,
+ "UVC non compliance: %s control %u on unit %u returned %d bytes when we expected %u.\n",
+ uvc_query_name(query), cs, unit, ret, size);
+ return 0;
+ }
+
if (ret != -EPIPE) {
dev_err(&dev->udev->dev,
"Failed to query (%s) UVC control %u on unit %u: %d (exp. %u).\n",
--
2.47.0.338.g60cca15819-goog
