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| author | Jacopo Mondi <jacopo@jmondi.org> | 2020-05-07 17:12:48 +0200 |
|---|---|---|
| committer | Mauro Carvalho Chehab <mchehab+huawei@kernel.org> | 2020-05-12 17:01:32 +0200 |
| commit | 18200e9e243d9095be953cf09cba29f9b3b5f262 (patch) | |
| tree | c1ae03d27aa5d21e99275eb8e7c03b63c02b6259 /Documentation/driver-api | |
| parent | media: ipu3.rst: fix a build warning (diff) | |
| download | linux-18200e9e243d9095be953cf09cba29f9b3b5f262.tar.xz linux-18200e9e243d9095be953cf09cba29f9b3b5f262.zip | |
media: 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>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Diffstat (limited to 'Documentation/driver-api')
| -rw-r--r-- | Documentation/driver-api/media/v4l2-subdev.rst | 9 |
1 files changed, 7 insertions, 2 deletions
diff --git a/Documentation/driver-api/media/v4l2-subdev.rst b/Documentation/driver-api/media/v4l2-subdev.rst index 29e07e23f888..41ccb3e5c707 100644 --- a/Documentation/driver-api/media/v4l2-subdev.rst +++ b/Documentation/driver-api/media/v4l2-subdev.rst @@ -275,8 +275,13 @@ system the .unbind() method is called. All three callbacks are optional. 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 |