Commit a965d202 authored by Mauro Carvalho Chehab's avatar Mauro Carvalho Chehab

[media] doc-rst: add documentation for uvcvideo

Convert it to ReST and add to media/v4l-drivers book.
Signed-off-by: default avatarMauro Carvalho Chehab <mchehab@s-opensource.com>
parent c0d01382
......@@ -39,4 +39,5 @@ License".
si4713
si476x
soc-camera
uvcvideo
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Linux USB Video Class (UVC) driver
==================================
The Linux USB Video Class (UVC) driver
======================================
This file documents some driver-specific aspects of the UVC driver, such as
driver-specific ioctls and implementation notes.
......@@ -11,7 +11,8 @@ linux-uvc-devel@lists.berlios.de.
Extension Unit (XU) support
---------------------------
1. Introduction
Introduction
~~~~~~~~~~~~
The UVC specification allows for vendor-specific extensions through extension
units (XUs). The Linux UVC driver supports extension unit controls (XU controls)
......@@ -31,7 +32,8 @@ maximum flexibility.
Both mechanisms complement each other and are described in more detail below.
2. Control mappings
Control mappings
~~~~~~~~~~~~~~~~
The UVC driver provides an API for user space applications to define so-called
control mappings at runtime. These allow for individual XU controls or byte
......@@ -82,7 +84,8 @@ For details on the UVCIOC_CTRL_QUERY ioctl please refer to the section titled
"IOCTL reference" below.
4. Security
Security
~~~~~~~~
The API doesn't currently provide a fine-grained access control facility. The
UVCIOC_CTRL_ADD and UVCIOC_CTRL_MAP ioctls require super user permissions.
......@@ -90,20 +93,24 @@ UVCIOC_CTRL_ADD and UVCIOC_CTRL_MAP ioctls require super user permissions.
Suggestions on how to improve this are welcome.
5. Debugging
Debugging
~~~~~~~~~
In order to debug problems related to XU controls or controls in general it is
recommended to enable the UVC_TRACE_CONTROL bit in the module parameter 'trace'.
This causes extra output to be written into the system log.
6. IOCTL reference
IOCTL reference
~~~~~~~~~~~~~~~
---- UVCIOC_CTRL_MAP - Map a UVC control to a V4L2 control ----
UVCIOC_CTRL_MAP - Map a UVC control to a V4L2 control
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Argument: struct uvc_xu_control_mapping
Description:
**Description**:
This ioctl creates a mapping between a UVC control or part of a UVC
control and a V4L2 control. Once mappings are defined, userspace
applications can access vendor-defined UVC control through the V4L2
......@@ -122,7 +129,8 @@ Description:
For signed integer V4L2 controls the data_type field should be set to
UVC_CTRL_DATA_TYPE_SIGNED. Other values are currently ignored.
Return value:
**Return value**:
On success 0 is returned. On error -1 is returned and errno is set
appropriately.
......@@ -137,7 +145,10 @@ Return value:
EEXIST
Mapping already exists.
Data types:
**Data types**:
.. code-block:: none
* struct uvc_xu_control_mapping
__u32 id V4L2 control identifier
......@@ -170,11 +181,12 @@ Data types:
UVC_CTRL_DATA_TYPE_BITMASK Bitmask
---- UVCIOC_CTRL_QUERY - Query a UVC XU control ----
UVCIOC_CTRL_QUERY - Query a UVC XU control
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Argument: struct uvc_xu_control_query
Description:
**Description**:
This ioctl queries a UVC XU control identified by its extension unit ID
and control selector.
......@@ -213,7 +225,8 @@ Description:
important for the result of the UVC_GET_LEN requests, which is always
returned as a little-endian 16-bit integer by the device.
Return value:
**Return value**:
On success 0 is returned. On error -1 is returned and errno is set
appropriately.
......@@ -229,7 +242,10 @@ Return value:
EFAULT
The data pointer references an inaccessible memory area.
Data types:
**Data types**:
.. code-block:: none
* struct uvc_xu_control_query
__u8 unit Extension unit ID
......
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