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@vger.kernel.org Fixes: a763b9fb58be ("media: uvcvideo: Do not return positive errors in uvc_query_ctrl()") Signed-off-by: Ricardo Ribalda ribalda@chromium.org --- drivers/media/usb/uvc/uvc_video.c | 19 +++++++++++++++++-- 1 file changed, 17 insertions(+), 2 deletions(-)

diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c index cd9c29532fb0..f125b3ba50f2 100644 --- a/drivers/media/usb/uvc/uvc_video.c +++ b/drivers/media/usb/uvc/uvc_video.c @@ -76,14 +76,29 @@ 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 + * for GET_DEF/MAX/MIN 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(&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", uvc_query_name(query), cs, unit, ret, size); - return ret < 0 ? ret : -EPIPE; + return ret ? ret : -EPIPE; }

/* Reuse data[0] to request the error code. */