| From afd6952c4dfb0d4945b496ef08b2f478d6f40097 Mon Sep 17 00:00:00 2001 |
| From: Jacopo Mondi <jacopo@jmondi.org> |
| Date: Tue, 7 Apr 2020 17:21:55 +0200 |
| Subject: [PATCH] Documentation: media: Update sub-device API intro |
| |
| Update the V4L2 sub-device userspace API introduction to provide more |
| details on why complex devices might want to register devnodes for the |
| connected subdevices. |
| |
| Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com> |
| Suggested-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> |
| Signed-off-by: Jacopo Mondi <jacopo@jmondi.org> |
| --- |
| Documentation/media/kapi/v4l2-subdev.rst | 9 +++++++-- |
| 1 file changed, 7 insertions(+), 2 deletions(-) |
| |
| --- a/Documentation/media/kapi/v4l2-subdev.rst |
| +++ b/Documentation/media/kapi/v4l2-subdev.rst |
| @@ -275,8 +275,13 @@ system the .unbind() method is called. A |
| V4L2 sub-device userspace API |
| ----------------------------- |
| |
| -Beside exposing a kernel API through the :c:type:`v4l2_subdev_ops` structure, |
| -V4L2 sub-devices can also be controlled directly by userspace applications. |
| +Bridge drivers traditionally expose one or multiple video nodes to userspace, |
| +and control subdevices through the :c:type:`v4l2_subdev_ops` operations in |
| +response to video node operations. This hides the complexity of the underlying |
| +hardware from applications. For complex devices, finer-grained control of the |
| +device than what the video nodes offer may be required. In those cases, bridge |
| +drivers that implement :ref:`the media controller API <media_controller>` may |
| +opt for making the subdevice operations directly accessible from userpace. |
| |
| Device nodes named ``v4l-subdev``\ *X* can be created in ``/dev`` to access |
| sub-devices directly. If a sub-device supports direct userspace configuration |