media: gspca/gl860: fix zero-length control requests

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>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

diff --git a/drivers/media/usb/gspca/gl860/gl860.c b/drivers/media/usb/gspca/gl860/gl860.c
index 2c05ea2598e7630a50c0ae13e7fe433f33947bde..ce4ee8bc75c85804364aa95701fac8a17d8458c5 100644 (file)
--- 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;
                }
        }