diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c index e00f38dd07d9..d2fe01bcd209 100644 --- a/drivers/media/usb/uvc/uvc_video.c +++ b/drivers/media/usb/uvc/uvc_video.c @@ -79,6 +79,27 @@ int uvc_query_ctrl(struct uvc_device *dev, u8 query, u8 unit, if (likely(ret == size)) return 0; + /* + * Some devices return shorter USB control packets than expected if the + * returned value can fit in less bytes. Zero all the bytes that the + * device has not written. + * + * This quirk is applied to all controls, regardless of their data type. + * Most controls are little-endian integers, in which case the missing + * bytes become 0 MSBs. For other data types, a different heuristic + * could be implemented if a device is found needing it. + * + * 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",