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1 | .. -*- coding: utf-8; mode: rst -*- |
2 | ||
af4a4d0d | 3 | .. _VIDIOC_G_CTRL: |
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4 | |
5 | ********************************** | |
6 | ioctl VIDIOC_G_CTRL, VIDIOC_S_CTRL | |
7 | ********************************** | |
8 | ||
15e7d615 | 9 | Name |
586027ce | 10 | ==== |
5377d91f | 11 | |
586027ce | 12 | VIDIOC_G_CTRL - VIDIOC_S_CTRL - Get or set the value of a control |
5377d91f | 13 | |
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14 | |
15 | Synopsis | |
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16 | ======== |
17 | ||
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18 | .. c:function:: int ioctl( int fd, VIDIOC_G_CTRL, struct v4l2_control *argp ) |
19 | :name: VIDIOC_G_CTRL | |
20 | ||
21 | .. c:function:: int ioctl( int fd, VIDIOC_S_CTRL, struct v4l2_control *argp ) | |
22 | :name: VIDIOC_S_CTRL | |
5377d91f | 23 | |
586027ce | 24 | |
15e7d615 | 25 | Arguments |
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26 | ========= |
27 | ||
28 | ``fd`` | |
29 | File descriptor returned by :ref:`open() <func-open>`. | |
30 | ||
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31 | ``argp`` |
32 | ||
33 | ||
15e7d615 | 34 | Description |
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35 | =========== |
36 | ||
37 | To get the current value of a control applications initialize the ``id`` | |
fc78c7c7 | 38 | field of a struct :c:type:`v4l2_control` and call the |
4e03cb76 | 39 | :ref:`VIDIOC_G_CTRL <VIDIOC_G_CTRL>` ioctl with a pointer to this structure. To change the |
5377d91f | 40 | value of a control applications initialize the ``id`` and ``value`` |
fc78c7c7 | 41 | fields of a struct :c:type:`v4l2_control` and call the |
2212ff25 | 42 | :ref:`VIDIOC_S_CTRL <VIDIOC_G_CTRL>` ioctl. |
5377d91f | 43 | |
cdb4af0f | 44 | When the ``id`` is invalid drivers return an ``EINVAL`` error code. When the |
5377d91f | 45 | ``value`` is out of bounds drivers can choose to take the closest valid |
cdb4af0f | 46 | value or return an ``ERANGE`` error code, whatever seems more appropriate. |
2212ff25 | 47 | However, :ref:`VIDIOC_S_CTRL <VIDIOC_G_CTRL>` is a write-only ioctl, it does not return the |
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48 | actual new value. If the ``value`` is inappropriate for the control |
49 | (e.g. if it refers to an unsupported menu index of a menu control), then | |
50 | EINVAL error code is returned as well. | |
51 | ||
52 | These ioctls work only with user controls. For other control classes the | |
4e03cb76 | 53 | :ref:`VIDIOC_G_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>`, |
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54 | :ref:`VIDIOC_S_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>` or |
55 | :ref:`VIDIOC_TRY_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>` must be used. | |
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56 | |
57 | ||
e8be7e97 | 58 | .. c:type:: v4l2_control |
5377d91f | 59 | |
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60 | .. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.7cm}| |
61 | ||
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62 | .. flat-table:: struct v4l2_control |
63 | :header-rows: 0 | |
64 | :stub-columns: 0 | |
65 | :widths: 1 1 2 | |
66 | ||
67 | ||
68 | - .. row 1 | |
69 | ||
70 | - __u32 | |
71 | ||
72 | - ``id`` | |
73 | ||
74 | - Identifies the control, set by the application. | |
75 | ||
76 | - .. row 2 | |
77 | ||
78 | - __s32 | |
79 | ||
80 | - ``value`` | |
81 | ||
82 | - New value or current value. | |
83 | ||
84 | ||
15e7d615 | 85 | Return Value |
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86 | ============ |
87 | ||
88 | On success 0 is returned, on error -1 and the ``errno`` variable is set | |
89 | appropriately. The generic error codes are described at the | |
90 | :ref:`Generic Error Codes <gen-errors>` chapter. | |
91 | ||
92 | EINVAL | |
e8be7e97 | 93 | The struct :c:type:`v4l2_control` ``id`` is invalid |
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94 | or the ``value`` is inappropriate for the given control (i.e. if a |
95 | menu item is selected that is not supported by the driver according | |
af4a4d0d | 96 | to :ref:`VIDIOC_QUERYMENU <VIDIOC_QUERYCTRL>`). |
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97 | |
98 | ERANGE | |
e8be7e97 | 99 | The struct :c:type:`v4l2_control` ``value`` is out of |
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100 | bounds. |
101 | ||
102 | EBUSY | |
103 | The control is temporarily not changeable, possibly because another | |
104 | applications took over control of the device function this control | |
105 | belongs to. | |
106 | ||
107 | EACCES | |
108 | Attempt to set a read-only control or to get a write-only control. |