[PATCH v3 4/8] media: uvcvideo: set error_idx to count on EACCESS

[Ricardo Ribalda]

If an error is found when validating the list of controls passed with
VIDIOC_G_EXT_CTRLS, then error_idx shall be set to ctrls->count to
indicate
to userspace that no actual hardware was touched.

It would have been much nicer of course if error_idx could point to the
control index that failed the validation, but sadly that's not how the
API was designed.

Fixes v4l2-compliance:
Control ioctls (Input 0):
                fail: v4l2-test-controls.cpp(645): invalid error index write 
only control
        test VIDIOC_G/S/TRY_EXT_CTRLS: FAIL

Signed-off-by: Ricardo Ribalda <riba...@chromium.org>
Reviewed-by: Hans Verkuil <hverkuil-ci...@xs4all.nl>
---
 drivers/media/usb/uvc/uvc_v4l2.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/media/usb/uvc/uvc_v4l2.c b/drivers/media/usb/uvc/uvc_v4l2.c
index 157310c0ca87..36eb48622d48 100644
--- a/drivers/media/usb/uvc/uvc_v4l2.c
+++ b/drivers/media/usb/uvc/uvc_v4l2.c
@@ -1073,7 +1073,8 @@ static int uvc_ioctl_g_ext_ctrls(struct file *file, void 
*fh,
                ret = uvc_ctrl_get(chain, ctrl);
                if (ret < 0) {
                        uvc_ctrl_rollback(handle);
-                       ctrls->error_idx = i;
+                       ctrls->error_idx = (ret == -EACCES) ?
+                                               ctrls->count : i;
                        return ret;
                }
        }
-- 
2.31.0.rc2.261.g7f71774620-goog