[PATCH 1/3] media: gspca/gl860: fix zero-length control requests

[Johan Hovold <johan@kernel.org>]

The direction of the pipe argument must match the request-type direction
bit or control requests may fail depending on the host-controller-driver
implementation.

Control transfers without a data stage are treated as OUT requests by
the USB stack and should be using usb_sndctrlpipe(). Failing to do so
will now trigger a warning.

Fix the gl860_RTx() helper so that zero-length control reads fail with
an error message instead. Note that there are no current callers that
would trigger this.

Fixes: 4f7cb8837cec ("V4L/DVB (12954): gspca - gl860: Addition of GL860 based webcams")
Signed-off-by: Johan Hovold <johan@kernel.org>
---
 drivers/media/usb/gspca/gl860/gl860.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/media/usb/gspca/gl860/gl860.c b/drivers/media/usb/gspca/gl860/gl860.c
index 2c05ea2598e7..ce4ee8bc75c8 100644
--- a/drivers/media/usb/gspca/gl860/gl860.c
+++ b/drivers/media/usb/gspca/gl860/gl860.c
@@ -561,8 +561,8 @@ int gl860_RTx(struct gspca_dev *gspca_dev,
 					len, 400 + 200 * (len > 1));
 			memcpy(pdata, gspca_dev->usb_buf, len);
 		} else {
-			r = usb_control_msg(udev, usb_rcvctrlpipe(udev, 0),
-					req, pref, val, index, NULL, len, 400);
+			gspca_err(gspca_dev, "zero-length read request\n");
+			r = -EINVAL;
 		}
 	}
 
-- 
2.26.3