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()")
Signed-off-by: Ricardo Ribalda <ribalda@xxxxxxxxxxxx>
---
drivers/media/usb/uvc/uvc_video.c | 16 +++++++++++++++-
1 file changed, 15 insertions(+), 1 deletion(-)
diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c
index cd9c29532fb0..e165850397a0 100644
--- a/drivers/media/usb/uvc/uvc_video.c
+++ b/drivers/media/usb/uvc/uvc_video.c
@@ -76,8 +76,22 @@ int uvc_query_ctrl(struct uvc_device *dev, u8 query, u8 unit,
ret = __uvc_query_ctrl(dev, query, unit, intfnum, cs, data, size,
UVC_CTRL_CONTROL_TIMEOUT);
- if (likely(ret == size))
+ if (ret > 0) {
+ if (size == ret)
+ return 0;
+
+ /*
+ * In UVC the data is represented in little-endian by default.
+ * Some devices return shorter control packages that expected
+ * if the return value can fit in less bytes.
+ * Zero all the bytes that the device have not written.
+ */
+ 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,
--
2.47.0.338.g60cca15819-goog
