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c2b66cafdf
Shorten the tables by removing row numbers in comments, allowing for
later insertion of rows with minimal diffs.
All changes have been generated by the following script.
import io
import re
import sys
def process_table(fname, data):
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data = re.sub(u'\n - \.\. row [0-9]+\n \.\. (_[A-Z0-9_`-]*:)', u'\n - .. \\1', data, flags = re.MULTILINE)
data = re.sub(u'\n - \.\. (_[A-Z0-9_`-]*:)\n -', u' * .. \\1\n\n -', data, flags = re.MULTILINE)
data = re.sub(u'^ - ', u' -', data, flags = re.MULTILINE)
data = re.sub(u'^(\t{1,2}) ', u'\\1', data, flags = re.MULTILINE)
return data
def process_file(fname, data):
buf = io.StringIO(data)
output = ''
in_table = False
table_separator = 0
for line in buf.readlines():
if line.find('.. flat-table::') != -1:
in_table = True
table = ''
elif in_table and not re.match('^[\t\n]|( )', line):
in_table = False
output += process_table(fname, table)
if in_table:
table += line
else:
output += line
if in_table:
in_table = False
output += process_table(fname, table)
return output
fname = sys.argv[1]
data = file(fname, 'rb').read().decode('utf-8')
data = process_file(fname, data)
file(fname, 'wb').write(data.encode('utf-8'))
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
374 lines
14 KiB
ReStructuredText
374 lines
14 KiB
ReStructuredText
.. -*- coding: utf-8; mode: rst -*-
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.. _VIDIOC_G_EXT_CTRLS:
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******************************************************************
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ioctl VIDIOC_G_EXT_CTRLS, VIDIOC_S_EXT_CTRLS, VIDIOC_TRY_EXT_CTRLS
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******************************************************************
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Name
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====
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VIDIOC_G_EXT_CTRLS - VIDIOC_S_EXT_CTRLS - VIDIOC_TRY_EXT_CTRLS - Get or set the value of several controls, try control values
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Synopsis
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========
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.. c:function:: int ioctl( int fd, VIDIOC_G_EXT_CTRLS, struct v4l2_ext_controls *argp )
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:name: VIDIOC_G_EXT_CTRLS
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.. c:function:: int ioctl( int fd, VIDIOC_S_EXT_CTRLS, struct v4l2_ext_controls *argp )
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:name: VIDIOC_S_EXT_CTRLS
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.. c:function:: int ioctl( int fd, VIDIOC_TRY_EXT_CTRLS, struct v4l2_ext_controls *argp )
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:name: VIDIOC_TRY_EXT_CTRLS
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Arguments
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=========
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``fd``
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File descriptor returned by :ref:`open() <func-open>`.
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``argp``
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Description
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===========
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These ioctls allow the caller to get or set multiple controls
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atomically. Control IDs are grouped into control classes (see
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:ref:`ctrl-class`) and all controls in the control array must belong
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to the same control class.
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Applications must always fill in the ``count``, ``which``, ``controls``
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and ``reserved`` fields of struct
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:c:type:`v4l2_ext_controls`, and initialize the
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struct :c:type:`v4l2_ext_control` array pointed to
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by the ``controls`` fields.
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To get the current value of a set of controls applications initialize
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the ``id``, ``size`` and ``reserved2`` fields of each struct
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:c:type:`v4l2_ext_control` and call the
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:ref:`VIDIOC_G_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>` ioctl. String controls controls must also set the
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``string`` field. Controls of compound types
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(``V4L2_CTRL_FLAG_HAS_PAYLOAD`` is set) must set the ``ptr`` field.
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If the ``size`` is too small to receive the control result (only
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relevant for pointer-type controls like strings), then the driver will
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set ``size`` to a valid value and return an ``ENOSPC`` error code. You
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should re-allocate the memory to this new size and try again. For the
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string type it is possible that the same issue occurs again if the
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string has grown in the meantime. It is recommended to call
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:ref:`VIDIOC_QUERYCTRL` first and use
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``maximum``\ +1 as the new ``size`` value. It is guaranteed that that is
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sufficient memory.
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N-dimensional arrays are set and retrieved row-by-row. You cannot set a
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partial array, all elements have to be set or retrieved. The total size
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is calculated as ``elems`` * ``elem_size``. These values can be obtained
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by calling :ref:`VIDIOC_QUERY_EXT_CTRL <VIDIOC_QUERYCTRL>`.
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To change the value of a set of controls applications initialize the
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``id``, ``size``, ``reserved2`` and ``value/value64/string/ptr`` fields
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of each struct :c:type:`v4l2_ext_control` and call
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the :ref:`VIDIOC_S_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>` ioctl. The controls will only be set if *all*
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control values are valid.
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To check if a set of controls have correct values applications
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initialize the ``id``, ``size``, ``reserved2`` and
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``value/value64/string/ptr`` fields of each struct
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:c:type:`v4l2_ext_control` and call the
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:ref:`VIDIOC_TRY_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>` ioctl. It is up to the driver whether wrong
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values are automatically adjusted to a valid value or if an error is
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returned.
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When the ``id`` or ``which`` is invalid drivers return an ``EINVAL`` error
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code. When the value is out of bounds drivers can choose to take the
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closest valid value or return an ``ERANGE`` error code, whatever seems more
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appropriate. In the first case the new value is set in struct
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:c:type:`v4l2_ext_control`. If the new control value
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is inappropriate (e.g. the given menu index is not supported by the menu
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control), then this will also result in an ``EINVAL`` error code error.
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The driver will only set/get these controls if all control values are
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correct. This prevents the situation where only some of the controls
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were set/get. Only low-level errors (e. g. a failed i2c command) can
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still cause this situation.
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.. tabularcolumns:: |p{1.2cm}|p{3.0cm}|p{1.5cm}|p{11.8cm}|
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.. c:type:: v4l2_ext_control
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.. cssclass: longtable
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.. flat-table:: struct v4l2_ext_control
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:header-rows: 0
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:stub-columns: 0
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:widths: 1 1 1 2
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* - __u32
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- ``id``
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-
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- Identifies the control, set by the application.
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* - __u32
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- ``size``
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-
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- The total size in bytes of the payload of this control. This is
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normally 0, but for pointer controls this should be set to the
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size of the memory containing the payload, or that will receive
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the payload. If :ref:`VIDIOC_G_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>` finds that this value is
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less than is required to store the payload result, then it is set
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to a value large enough to store the payload result and ``ENOSPC`` is
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returned.
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.. note::
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For string controls, this ``size`` field should
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not be confused with the length of the string. This field refers
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to the size of the memory that contains the string. The actual
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*length* of the string may well be much smaller.
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* - __u32
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- ``reserved2``\ [1]
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-
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- Reserved for future extensions. Drivers and applications must set
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the array to zero.
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* - union
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- (anonymous)
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* -
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- __s32
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- ``value``
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- New value or current value. Valid if this control is not of type
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``V4L2_CTRL_TYPE_INTEGER64`` and ``V4L2_CTRL_FLAG_HAS_PAYLOAD`` is
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not set.
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* -
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- __s64
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- ``value64``
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- New value or current value. Valid if this control is of type
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``V4L2_CTRL_TYPE_INTEGER64`` and ``V4L2_CTRL_FLAG_HAS_PAYLOAD`` is
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not set.
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* -
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- char *
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- ``string``
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- A pointer to a string. Valid if this control is of type
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``V4L2_CTRL_TYPE_STRING``.
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* -
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- __u8 *
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- ``p_u8``
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- A pointer to a matrix control of unsigned 8-bit values. Valid if
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this control is of type ``V4L2_CTRL_TYPE_U8``.
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* -
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- __u16 *
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- ``p_u16``
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- A pointer to a matrix control of unsigned 16-bit values. Valid if
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this control is of type ``V4L2_CTRL_TYPE_U16``.
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* -
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- __u32 *
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- ``p_u32``
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- A pointer to a matrix control of unsigned 32-bit values. Valid if
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this control is of type ``V4L2_CTRL_TYPE_U32``.
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* -
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- void *
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- ``ptr``
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- A pointer to a compound type which can be an N-dimensional array
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and/or a compound type (the control's type is >=
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``V4L2_CTRL_COMPOUND_TYPES``). Valid if
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``V4L2_CTRL_FLAG_HAS_PAYLOAD`` is set for this control.
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.. tabularcolumns:: |p{4.0cm}|p{2.0cm}|p{2.0cm}|p{8.5cm}|
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.. c:type:: v4l2_ext_controls
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.. cssclass:: longtable
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.. flat-table:: struct v4l2_ext_controls
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:header-rows: 0
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:stub-columns: 0
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:widths: 1 1 2 1
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* - union
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- (anonymous)
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* -
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- __u32
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- ``ctrl_class``
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- The control class to which all controls belong, see
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:ref:`ctrl-class`. Drivers that use a kernel framework for
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handling controls will also accept a value of 0 here, meaning that
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the controls can belong to any control class. Whether drivers
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support this can be tested by setting ``ctrl_class`` to 0 and
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calling :ref:`VIDIOC_TRY_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>` with a ``count`` of 0. If that
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succeeds, then the driver supports this feature.
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* -
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- __u32
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- ``which``
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- Which value of the control to get/set/try.
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``V4L2_CTRL_WHICH_CUR_VAL`` will return the current value of the
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control and ``V4L2_CTRL_WHICH_DEF_VAL`` will return the default
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value of the control.
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.. note::
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You can only get the default value of the control,
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you cannot set or try it.
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For backwards compatibility you can also use a control class here
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(see :ref:`ctrl-class`). In that case all controls have to
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belong to that control class. This usage is deprecated, instead
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just use ``V4L2_CTRL_WHICH_CUR_VAL``. There are some very old
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drivers that do not yet support ``V4L2_CTRL_WHICH_CUR_VAL`` and
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that require a control class here. You can test for such drivers
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by setting ctrl_class to ``V4L2_CTRL_WHICH_CUR_VAL`` and calling
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VIDIOC_TRY_EXT_CTRLS with a count of 0. If that fails, then the
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driver does not support ``V4L2_CTRL_WHICH_CUR_VAL``.
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* - __u32
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- ``count``
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- The number of controls in the controls array. May also be zero.
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* - __u32
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- ``error_idx``
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- Set by the driver in case of an error. If the error is associated
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with a particular control, then ``error_idx`` is set to the index
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of that control. If the error is not related to a specific
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control, or the validation step failed (see below), then
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``error_idx`` is set to ``count``. The value is undefined if the
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ioctl returned 0 (success).
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Before controls are read from/written to hardware a validation
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step takes place: this checks if all controls in the list are
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valid controls, if no attempt is made to write to a read-only
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control or read from a write-only control, and any other up-front
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checks that can be done without accessing the hardware. The exact
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validations done during this step are driver dependent since some
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checks might require hardware access for some devices, thus making
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it impossible to do those checks up-front. However, drivers should
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make a best-effort to do as many up-front checks as possible.
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This check is done to avoid leaving the hardware in an
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inconsistent state due to easy-to-avoid problems. But it leads to
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another problem: the application needs to know whether an error
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came from the validation step (meaning that the hardware was not
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touched) or from an error during the actual reading from/writing
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to hardware.
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The, in hindsight quite poor, solution for that is to set
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``error_idx`` to ``count`` if the validation failed. This has the
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unfortunate side-effect that it is not possible to see which
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control failed the validation. If the validation was successful
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and the error happened while accessing the hardware, then
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``error_idx`` is less than ``count`` and only the controls up to
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``error_idx-1`` were read or written correctly, and the state of
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the remaining controls is undefined.
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Since :ref:`VIDIOC_TRY_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>` does not access hardware there is
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also no need to handle the validation step in this special way, so
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``error_idx`` will just be set to the control that failed the
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validation step instead of to ``count``. This means that if
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:ref:`VIDIOC_S_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>` fails with ``error_idx`` set to ``count``,
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then you can call :ref:`VIDIOC_TRY_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>` to try to discover the
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actual control that failed the validation step. Unfortunately,
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there is no ``TRY`` equivalent for :ref:`VIDIOC_G_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>`.
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* - __u32
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- ``reserved``\ [2]
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- Reserved for future extensions.
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Drivers and applications must set the array to zero.
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* - struct :c:type:`v4l2_ext_control` *
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- ``controls``
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- Pointer to an array of ``count`` v4l2_ext_control structures.
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Ignored if ``count`` equals zero.
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.. tabularcolumns:: |p{6.6cm}|p{2.2cm}|p{8.7cm}|
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.. _ctrl-class:
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.. flat-table:: Control classes
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:header-rows: 0
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:stub-columns: 0
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:widths: 3 1 4
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* - ``V4L2_CTRL_CLASS_USER``
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- 0x980000
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- The class containing user controls. These controls are described
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in :ref:`control`. All controls that can be set using the
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:ref:`VIDIOC_S_CTRL <VIDIOC_G_CTRL>` and
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:ref:`VIDIOC_G_CTRL <VIDIOC_G_CTRL>` ioctl belong to this
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class.
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* - ``V4L2_CTRL_CLASS_MPEG``
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- 0x990000
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- The class containing MPEG compression controls. These controls are
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described in :ref:`mpeg-controls`.
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* - ``V4L2_CTRL_CLASS_CAMERA``
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- 0x9a0000
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- The class containing camera controls. These controls are described
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in :ref:`camera-controls`.
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* - ``V4L2_CTRL_CLASS_FM_TX``
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- 0x9b0000
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- The class containing FM Transmitter (FM TX) controls. These
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controls are described in :ref:`fm-tx-controls`.
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* - ``V4L2_CTRL_CLASS_FLASH``
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- 0x9c0000
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- The class containing flash device controls. These controls are
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described in :ref:`flash-controls`.
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* - ``V4L2_CTRL_CLASS_JPEG``
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- 0x9d0000
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- The class containing JPEG compression controls. These controls are
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described in :ref:`jpeg-controls`.
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* - ``V4L2_CTRL_CLASS_IMAGE_SOURCE``
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- 0x9e0000
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- The class containing image source controls. These controls are
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described in :ref:`image-source-controls`.
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* - ``V4L2_CTRL_CLASS_IMAGE_PROC``
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- 0x9f0000
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- The class containing image processing controls. These controls are
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described in :ref:`image-process-controls`.
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* - ``V4L2_CTRL_CLASS_FM_RX``
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- 0xa10000
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- The class containing FM Receiver (FM RX) controls. These controls
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are described in :ref:`fm-rx-controls`.
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* - ``V4L2_CTRL_CLASS_RF_TUNER``
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- 0xa20000
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- The class containing RF tuner controls. These controls are
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described in :ref:`rf-tuner-controls`.
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Return Value
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============
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On success 0 is returned, on error -1 and the ``errno`` variable is set
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appropriately. The generic error codes are described at the
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:ref:`Generic Error Codes <gen-errors>` chapter.
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EINVAL
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The struct :c:type:`v4l2_ext_control` ``id`` is
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invalid, the struct :c:type:`v4l2_ext_controls`
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``which`` is invalid, or the struct
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:c:type:`v4l2_ext_control` ``value`` was
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inappropriate (e.g. the given menu index is not supported by the
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driver). This error code is also returned by the
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:ref:`VIDIOC_S_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>` and :ref:`VIDIOC_TRY_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>` ioctls if two or
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more control values are in conflict.
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ERANGE
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The struct :c:type:`v4l2_ext_control` ``value``
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is out of bounds.
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EBUSY
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The control is temporarily not changeable, possibly because another
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applications took over control of the device function this control
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belongs to.
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ENOSPC
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The space reserved for the control's payload is insufficient. The
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field ``size`` is set to a value that is enough to store the payload
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and this error code is returned.
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EACCES
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Attempt to try or set a read-only control or to get a write-only
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control.
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