media: docs: Document the behaviour of uvcvideo driver

The uvc driver relies on the camera firmware to keep the control states
and therefore is not capable of changing an inactive control.

Allow returning -EACCES in those cases.

Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

diff --git a/Documentation/userspace-api/media/v4l/vidioc-g-ctrl.rst b/Documentation/userspace-api/media/v4l/vidioc-g-ctrl.rst
index 80e8c63..fd09677 100644 (file)
--- a/Documentation/userspace-api/media/v4l/vidioc-g-ctrl.rst
+++ b/Documentation/userspace-api/media/v4l/vidioc-g-ctrl.rst
@@ -95,3 +95,6 @@ EBUSY
 
 EACCES
     Attempt to set a read-only control or to get a write-only control.
+
+    Or if there is an attempt to set an inactive control and the driver is
+    not capable of caching the new value until the control is active again.

diff --git a/Documentation/userspace-api/media/v4l/vidioc-g-ext-ctrls.rst b/Documentation/userspace-api/media/v4l/vidioc-g-ext-ctrls.rst
index 2d6bc8d..fdde0ae 100644 (file)
--- a/Documentation/userspace-api/media/v4l/vidioc-g-ext-ctrls.rst
+++ b/Documentation/userspace-api/media/v4l/vidioc-g-ext-ctrls.rst
@@ -470,3 +470,6 @@ EACCES
 
     Or the ``which`` field was set to ``V4L2_CTRL_WHICH_REQUEST_VAL`` but the
     device does not support requests.
+
+    Or if there is an attempt to set an inactive control and the driver is
+    not capable of caching the new value until the control is active again.