[PATCH v5 12/13] media: v4l2-ioctl: Set error_idx to the right value

[Ricardo Ribalda <ribalda@chromium.org>]

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):
	warn: v4l2-test-controls.cpp(834): error_idx should be equal to count
	warn: v4l2-test-controls.cpp(855): error_idx should be equal to count
	test VIDIOC_G/S/TRY_EXT_CTRLS: OK

Fixes: 6fa6f831f095 ("media: v4l2-ctrls: add core request support")
Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
---
 drivers/media/v4l2-core/v4l2-ioctl.c | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c b/drivers/media/v4l2-core/v4l2-ioctl.c
index 9406e90ff805..936ae21a0e0e 100644
--- a/drivers/media/v4l2-core/v4l2-ioctl.c
+++ b/drivers/media/v4l2-core/v4l2-ioctl.c
@@ -2294,8 +2294,12 @@ static int v4l_g_ext_ctrls(const struct v4l2_ioctl_ops *ops,
 					vfd, vfd->v4l2_dev->mdev, p);
 	if (ops->vidioc_g_ext_ctrls == NULL)
 		return -ENOTTY;
-	return check_ext_ctrls(p, 0) ? ops->vidioc_g_ext_ctrls(file, fh, p) :
-					-EINVAL;
+
+	if (check_ext_ctrls(p, 0))
+		return ops->vidioc_g_ext_ctrls(file, fh, p);
+
+	p->error_idx = p->count;
+	return -EINVAL;
 }
 
 static int v4l_s_ext_ctrls(const struct v4l2_ioctl_ops *ops,
@@ -2315,8 +2319,11 @@ static int v4l_s_ext_ctrls(const struct v4l2_ioctl_ops *ops,
 					vfd, vfd->v4l2_dev->mdev, p);
 	if (ops->vidioc_s_ext_ctrls == NULL)
 		return -ENOTTY;
-	return check_ext_ctrls(p, 0) ? ops->vidioc_s_ext_ctrls(file, fh, p) :
-					-EINVAL;
+	if (check_ext_ctrls(p, 0))
+		return ops->vidioc_s_ext_ctrls(file, fh, p);
+
+	p->error_idx = p->count;
+	return -EINVAL;
 }
 
 static int v4l_try_ext_ctrls(const struct v4l2_ioctl_ops *ops,
-- 
2.31.0.rc2.261.g7f71774620-goog