From afd6952c4dfb0d4945b496ef08b2f478d6f40097 Mon Sep 17 00:00:00 2001 From: Jacopo Mondi 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 Suggested-by: Laurent Pinchart Signed-off-by: Jacopo Mondi --- 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 ` 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