| b.liu | e958203 | 2025-04-17 19:18:16 +0800 | [diff] [blame^] | 1 | From afd6952c4dfb0d4945b496ef08b2f478d6f40097 Mon Sep 17 00:00:00 2001 |
| 2 | From: Jacopo Mondi <jacopo@jmondi.org> |
| 3 | Date: Tue, 7 Apr 2020 17:21:55 +0200 |
| 4 | Subject: [PATCH] Documentation: media: Update sub-device API intro |
| 5 | |
| 6 | Update the V4L2 sub-device userspace API introduction to provide more |
| 7 | details on why complex devices might want to register devnodes for the |
| 8 | connected subdevices. |
| 9 | |
| 10 | Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com> |
| 11 | Suggested-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> |
| 12 | Signed-off-by: Jacopo Mondi <jacopo@jmondi.org> |
| 13 | --- |
| 14 | Documentation/media/kapi/v4l2-subdev.rst | 9 +++++++-- |
| 15 | 1 file changed, 7 insertions(+), 2 deletions(-) |
| 16 | |
| 17 | --- a/Documentation/media/kapi/v4l2-subdev.rst |
| 18 | +++ b/Documentation/media/kapi/v4l2-subdev.rst |
| 19 | @@ -275,8 +275,13 @@ system the .unbind() method is called. A |
| 20 | V4L2 sub-device userspace API |
| 21 | ----------------------------- |
| 22 | |
| 23 | -Beside exposing a kernel API through the :c:type:`v4l2_subdev_ops` structure, |
| 24 | -V4L2 sub-devices can also be controlled directly by userspace applications. |
| 25 | +Bridge drivers traditionally expose one or multiple video nodes to userspace, |
| 26 | +and control subdevices through the :c:type:`v4l2_subdev_ops` operations in |
| 27 | +response to video node operations. This hides the complexity of the underlying |
| 28 | +hardware from applications. For complex devices, finer-grained control of the |
| 29 | +device than what the video nodes offer may be required. In those cases, bridge |
| 30 | +drivers that implement :ref:`the media controller API <media_controller>` may |
| 31 | +opt for making the subdevice operations directly accessible from userpace. |
| 32 | |
| 33 | Device nodes named ``v4l-subdev``\ *X* can be created in ``/dev`` to access |
| 34 | sub-devices directly. If a sub-device supports direct userspace configuration |