1 .. SPDX-License-Identifier: GFDL-1.1-no-invari 1 .. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later 2 .. c:namespace:: V4L 2 .. c:namespace:: V4L 3 3 4 .. _VIDIOC_QUERYCTRL: 4 .. _VIDIOC_QUERYCTRL: 5 5 6 ********************************************** 6 ******************************************************************* 7 ioctls VIDIOC_QUERYCTRL, VIDIOC_QUERY_EXT_CTRL 7 ioctls VIDIOC_QUERYCTRL, VIDIOC_QUERY_EXT_CTRL and VIDIOC_QUERYMENU 8 ********************************************** 8 ******************************************************************* 9 9 10 Name 10 Name 11 ==== 11 ==== 12 12 13 VIDIOC_QUERYCTRL - VIDIOC_QUERY_EXT_CTRL - VID 13 VIDIOC_QUERYCTRL - VIDIOC_QUERY_EXT_CTRL - VIDIOC_QUERYMENU - Enumerate controls and menu control items 14 14 15 Synopsis 15 Synopsis 16 ======== 16 ======== 17 17 18 ``int ioctl(int fd, int VIDIOC_QUERYCTRL, stru 18 ``int ioctl(int fd, int VIDIOC_QUERYCTRL, struct v4l2_queryctrl *argp)`` 19 19 20 .. c:macro:: VIDIOC_QUERY_EXT_CTRL 20 .. c:macro:: VIDIOC_QUERY_EXT_CTRL 21 21 22 ``int ioctl(int fd, VIDIOC_QUERY_EXT_CTRL, str 22 ``int ioctl(int fd, VIDIOC_QUERY_EXT_CTRL, struct v4l2_query_ext_ctrl *argp)`` 23 23 24 .. c:macro:: VIDIOC_QUERYMENU 24 .. c:macro:: VIDIOC_QUERYMENU 25 25 26 ``int ioctl(int fd, VIDIOC_QUERYMENU, struct v 26 ``int ioctl(int fd, VIDIOC_QUERYMENU, struct v4l2_querymenu *argp)`` 27 27 28 Arguments 28 Arguments 29 ========= 29 ========= 30 30 31 ``fd`` 31 ``fd`` 32 File descriptor returned by :c:func:`open( 32 File descriptor returned by :c:func:`open()`. 33 33 34 ``argp`` 34 ``argp`` 35 Pointer to struct :c:type:`v4l2_queryctrl` 35 Pointer to struct :c:type:`v4l2_queryctrl`, :c:type:`v4l2_query_ext_ctrl` 36 or :c:type:`v4l2_querymenu` (depending on 36 or :c:type:`v4l2_querymenu` (depending on the ioctl). 37 37 38 Description 38 Description 39 =========== 39 =========== 40 40 41 To query the attributes of a control applicati 41 To query the attributes of a control applications set the ``id`` field 42 of a struct :ref:`v4l2_queryctrl <v4l2-queryct 42 of a struct :ref:`v4l2_queryctrl <v4l2-queryctrl>` and call the 43 ``VIDIOC_QUERYCTRL`` ioctl with a pointer to t 43 ``VIDIOC_QUERYCTRL`` ioctl with a pointer to this structure. The driver 44 fills the rest of the structure or returns an 44 fills the rest of the structure or returns an ``EINVAL`` error code when the 45 ``id`` is invalid. 45 ``id`` is invalid. 46 46 47 It is possible to enumerate controls by callin 47 It is possible to enumerate controls by calling ``VIDIOC_QUERYCTRL`` 48 with successive ``id`` values starting from `` 48 with successive ``id`` values starting from ``V4L2_CID_BASE`` up to and 49 exclusive ``V4L2_CID_LASTP1``. Drivers may ret 49 exclusive ``V4L2_CID_LASTP1``. Drivers may return ``EINVAL`` if a control in 50 this range is not supported. Further applicati 50 this range is not supported. Further applications can enumerate private 51 controls, which are not defined in this specif 51 controls, which are not defined in this specification, by starting at 52 ``V4L2_CID_PRIVATE_BASE`` and incrementing ``i 52 ``V4L2_CID_PRIVATE_BASE`` and incrementing ``id`` until the driver 53 returns ``EINVAL``. 53 returns ``EINVAL``. 54 54 55 In both cases, when the driver sets the ``V4L2 55 In both cases, when the driver sets the ``V4L2_CTRL_FLAG_DISABLED`` flag 56 in the ``flags`` field this control is permane 56 in the ``flags`` field this control is permanently disabled and should 57 be ignored by the application. [#f1]_ 57 be ignored by the application. [#f1]_ 58 58 59 When the application ORs ``id`` with ``V4L2_CT 59 When the application ORs ``id`` with ``V4L2_CTRL_FLAG_NEXT_CTRL`` the 60 driver returns the next supported non-compound 60 driver returns the next supported non-compound control, or ``EINVAL`` if 61 there is none. In addition, the ``V4L2_CTRL_FL 61 there is none. In addition, the ``V4L2_CTRL_FLAG_NEXT_COMPOUND`` flag 62 can be specified to enumerate all compound con 62 can be specified to enumerate all compound controls (i.e. controls with 63 type ≥ ``V4L2_CTRL_COMPOUND_TYPES`` and/or a 63 type ≥ ``V4L2_CTRL_COMPOUND_TYPES`` and/or array control, in other words 64 controls that contain more than one value). Sp 64 controls that contain more than one value). Specify both 65 ``V4L2_CTRL_FLAG_NEXT_CTRL`` and ``V4L2_CTRL_F 65 ``V4L2_CTRL_FLAG_NEXT_CTRL`` and ``V4L2_CTRL_FLAG_NEXT_COMPOUND`` in 66 order to enumerate all controls, compound or n 66 order to enumerate all controls, compound or not. Drivers which do not 67 support these flags yet always return ``EINVAL 67 support these flags yet always return ``EINVAL``. 68 68 69 The ``VIDIOC_QUERY_EXT_CTRL`` ioctl was introd 69 The ``VIDIOC_QUERY_EXT_CTRL`` ioctl was introduced in order to better 70 support controls that can use compound types, 70 support controls that can use compound types, and to expose additional 71 control information that cannot be returned in 71 control information that cannot be returned in struct 72 :ref:`v4l2_queryctrl <v4l2-queryctrl>` since t 72 :ref:`v4l2_queryctrl <v4l2-queryctrl>` since that structure is full. 73 73 74 ``VIDIOC_QUERY_EXT_CTRL`` is used in the same 74 ``VIDIOC_QUERY_EXT_CTRL`` is used in the same way as 75 ``VIDIOC_QUERYCTRL``, except that the ``reserv 75 ``VIDIOC_QUERYCTRL``, except that the ``reserved`` array must be zeroed 76 as well. 76 as well. 77 77 78 Additional information is required for menu co 78 Additional information is required for menu controls: the names of the 79 menu items. To query them applications set the 79 menu items. To query them applications set the ``id`` and ``index`` 80 fields of struct :ref:`v4l2_querymenu <v4l2-qu 80 fields of struct :ref:`v4l2_querymenu <v4l2-querymenu>` and call the 81 ``VIDIOC_QUERYMENU`` ioctl with a pointer to t 81 ``VIDIOC_QUERYMENU`` ioctl with a pointer to this structure. The driver 82 fills the rest of the structure or returns an 82 fills the rest of the structure or returns an ``EINVAL`` error code when the 83 ``id`` or ``index`` is invalid. Menu items are 83 ``id`` or ``index`` is invalid. Menu items are enumerated by calling 84 ``VIDIOC_QUERYMENU`` with successive ``index`` 84 ``VIDIOC_QUERYMENU`` with successive ``index`` values from struct 85 :ref:`v4l2_queryctrl <v4l2-queryctrl>` ``minim 85 :ref:`v4l2_queryctrl <v4l2-queryctrl>` ``minimum`` to ``maximum``, 86 inclusive. 86 inclusive. 87 87 88 .. note:: 88 .. note:: 89 89 90 It is possible for ``VIDIOC_QUERYMENU`` to 90 It is possible for ``VIDIOC_QUERYMENU`` to return 91 an ``EINVAL`` error code for some indices b 91 an ``EINVAL`` error code for some indices between ``minimum`` and 92 ``maximum``. In that case that particular m 92 ``maximum``. In that case that particular menu item is not supported by 93 this driver. Also note that the ``minimum`` 93 this driver. Also note that the ``minimum`` value is not necessarily 0. 94 94 95 See also the examples in :ref:`control`. 95 See also the examples in :ref:`control`. 96 96 97 .. tabularcolumns:: |p{1.2cm}|p{3.6cm}|p{12.5c 97 .. tabularcolumns:: |p{1.2cm}|p{3.6cm}|p{12.5cm}| 98 98 99 .. _v4l2-queryctrl: 99 .. _v4l2-queryctrl: 100 100 101 .. cssclass:: longtable 101 .. cssclass:: longtable 102 102 103 .. flat-table:: struct v4l2_queryctrl 103 .. flat-table:: struct v4l2_queryctrl 104 :header-rows: 0 104 :header-rows: 0 105 :stub-columns: 0 105 :stub-columns: 0 106 :widths: 1 1 2 106 :widths: 1 1 2 107 107 108 * - __u32 108 * - __u32 109 - ``id`` 109 - ``id`` 110 - Identifies the control, set by the app 110 - Identifies the control, set by the application. See 111 :ref:`control-id` for predefined IDs. 111 :ref:`control-id` for predefined IDs. When the ID is ORed with 112 V4L2_CTRL_FLAG_NEXT_CTRL the driver cl 112 V4L2_CTRL_FLAG_NEXT_CTRL the driver clears the flag and 113 returns the first control with a highe 113 returns the first control with a higher ID. Drivers which do not 114 support this flag yet always return an 114 support this flag yet always return an ``EINVAL`` error code. 115 * - __u32 115 * - __u32 116 - ``type`` 116 - ``type`` 117 - Type of control, see :c:type:`v4l2_ctr 117 - Type of control, see :c:type:`v4l2_ctrl_type`. 118 * - __u8 118 * - __u8 119 - ``name``\ [32] 119 - ``name``\ [32] 120 - Name of the control, a NUL-terminated 120 - Name of the control, a NUL-terminated ASCII string. This 121 information is intended for the user. 121 information is intended for the user. 122 * - __s32 122 * - __s32 123 - ``minimum`` 123 - ``minimum`` 124 - Minimum value, inclusive. This field g 124 - Minimum value, inclusive. This field gives a lower bound for the 125 control. See enum :c:type:`v4l2_ctrl_t 125 control. See enum :c:type:`v4l2_ctrl_type` how 126 the minimum value is to be used for ea 126 the minimum value is to be used for each possible control type. 127 Note that this a signed 32-bit value. 127 Note that this a signed 32-bit value. 128 * - __s32 128 * - __s32 129 - ``maximum`` 129 - ``maximum`` 130 - Maximum value, inclusive. This field g 130 - Maximum value, inclusive. This field gives an upper bound for the 131 control. See enum :c:type:`v4l2_ctrl_t 131 control. See enum :c:type:`v4l2_ctrl_type` how 132 the maximum value is to be used for ea 132 the maximum value is to be used for each possible control type. 133 Note that this a signed 32-bit value. 133 Note that this a signed 32-bit value. 134 * - __s32 134 * - __s32 135 - ``step`` 135 - ``step`` 136 - This field gives a step size for the c 136 - This field gives a step size for the control. See enum 137 :c:type:`v4l2_ctrl_type` how the step 137 :c:type:`v4l2_ctrl_type` how the step value is 138 to be used for each possible control t 138 to be used for each possible control type. Note that this an 139 unsigned 32-bit value. 139 unsigned 32-bit value. 140 140 141 Generally drivers should not scale har 141 Generally drivers should not scale hardware control values. It may 142 be necessary for example when the ``na 142 be necessary for example when the ``name`` or ``id`` imply a 143 particular unit and the hardware actua 143 particular unit and the hardware actually accepts only multiples 144 of said unit. If so, drivers must take 144 of said unit. If so, drivers must take care values are properly 145 rounded when scaling, such that errors 145 rounded when scaling, such that errors will not accumulate on 146 repeated read-write cycles. 146 repeated read-write cycles. 147 147 148 This field gives the smallest change o 148 This field gives the smallest change of an integer control 149 actually affecting hardware. Often the 149 actually affecting hardware. Often the information is needed when 150 the user can change controls by keyboa 150 the user can change controls by keyboard or GUI buttons, rather 151 than a slider. When for example a hard 151 than a slider. When for example a hardware register accepts values 152 0-511 and the driver reports 0-65535, 152 0-511 and the driver reports 0-65535, step should be 128. 153 153 154 Note that although signed, the step va 154 Note that although signed, the step value is supposed to be always 155 positive. 155 positive. 156 * - __s32 156 * - __s32 157 - ``default_value`` 157 - ``default_value`` 158 - The default value of a ``V4L2_CTRL_TYP 158 - The default value of a ``V4L2_CTRL_TYPE_INTEGER``, ``_BOOLEAN``, 159 ``_BITMASK``, ``_MENU`` or ``_INTEGER_ 159 ``_BITMASK``, ``_MENU`` or ``_INTEGER_MENU`` control. Not valid 160 for other types of controls. 160 for other types of controls. 161 161 162 .. note:: 162 .. note:: 163 163 164 Drivers reset controls to their def 164 Drivers reset controls to their default value only when 165 the driver is first loaded, never a 165 the driver is first loaded, never afterwards. 166 * - __u32 166 * - __u32 167 - ``flags`` 167 - ``flags`` 168 - Control flags, see :ref:`control-flags 168 - Control flags, see :ref:`control-flags`. 169 * - __u32 169 * - __u32 170 - ``reserved``\ [2] 170 - ``reserved``\ [2] 171 - Reserved for future extensions. Driver 171 - Reserved for future extensions. Drivers must set the array to 172 zero. 172 zero. 173 173 174 174 175 .. tabularcolumns:: |p{1.2cm}|p{5.5cm}|p{10.6c 175 .. tabularcolumns:: |p{1.2cm}|p{5.5cm}|p{10.6cm}| 176 176 177 .. _v4l2-query-ext-ctrl: 177 .. _v4l2-query-ext-ctrl: 178 178 179 .. cssclass:: longtable 179 .. cssclass:: longtable 180 180 181 .. flat-table:: struct v4l2_query_ext_ctrl 181 .. flat-table:: struct v4l2_query_ext_ctrl 182 :header-rows: 0 182 :header-rows: 0 183 :stub-columns: 0 183 :stub-columns: 0 184 :widths: 1 1 2 184 :widths: 1 1 2 185 185 186 * - __u32 186 * - __u32 187 - ``id`` 187 - ``id`` 188 - Identifies the control, set by the app 188 - Identifies the control, set by the application. See 189 :ref:`control-id` for predefined IDs. 189 :ref:`control-id` for predefined IDs. When the ID is ORed with 190 ``V4L2_CTRL_FLAG_NEXT_CTRL`` the drive 190 ``V4L2_CTRL_FLAG_NEXT_CTRL`` the driver clears the flag and 191 returns the first non-compound control 191 returns the first non-compound control with a higher ID. When the 192 ID is ORed with ``V4L2_CTRL_FLAG_NEXT_ 192 ID is ORed with ``V4L2_CTRL_FLAG_NEXT_COMPOUND`` the driver clears 193 the flag and returns the first compoun 193 the flag and returns the first compound control with a higher ID. 194 Set both to get the first control (com 194 Set both to get the first control (compound or not) with a higher 195 ID. 195 ID. 196 * - __u32 196 * - __u32 197 - ``type`` 197 - ``type`` 198 - Type of control, see :c:type:`v4l2_ctr 198 - Type of control, see :c:type:`v4l2_ctrl_type`. 199 * - char 199 * - char 200 - ``name``\ [32] 200 - ``name``\ [32] 201 - Name of the control, a NUL-terminated 201 - Name of the control, a NUL-terminated ASCII string. This 202 information is intended for the user. 202 information is intended for the user. 203 * - __s64 203 * - __s64 204 - ``minimum`` 204 - ``minimum`` 205 - Minimum value, inclusive. This field g 205 - Minimum value, inclusive. This field gives a lower bound for the 206 control. See enum :c:type:`v4l2_ctrl_t 206 control. See enum :c:type:`v4l2_ctrl_type` how 207 the minimum value is to be used for ea 207 the minimum value is to be used for each possible control type. 208 Note that this a signed 64-bit value. 208 Note that this a signed 64-bit value. 209 * - __s64 209 * - __s64 210 - ``maximum`` 210 - ``maximum`` 211 - Maximum value, inclusive. This field g 211 - Maximum value, inclusive. This field gives an upper bound for the 212 control. See enum :c:type:`v4l2_ctrl_t 212 control. See enum :c:type:`v4l2_ctrl_type` how 213 the maximum value is to be used for ea 213 the maximum value is to be used for each possible control type. 214 Note that this a signed 64-bit value. 214 Note that this a signed 64-bit value. 215 * - __u64 215 * - __u64 216 - ``step`` 216 - ``step`` 217 - This field gives a step size for the c 217 - This field gives a step size for the control. See enum 218 :c:type:`v4l2_ctrl_type` how the step 218 :c:type:`v4l2_ctrl_type` how the step value is 219 to be used for each possible control t 219 to be used for each possible control type. Note that this an 220 unsigned 64-bit value. 220 unsigned 64-bit value. 221 221 222 Generally drivers should not scale har 222 Generally drivers should not scale hardware control values. It may 223 be necessary for example when the ``na 223 be necessary for example when the ``name`` or ``id`` imply a 224 particular unit and the hardware actua 224 particular unit and the hardware actually accepts only multiples 225 of said unit. If so, drivers must take 225 of said unit. If so, drivers must take care values are properly 226 rounded when scaling, such that errors 226 rounded when scaling, such that errors will not accumulate on 227 repeated read-write cycles. 227 repeated read-write cycles. 228 228 229 This field gives the smallest change o 229 This field gives the smallest change of an integer control 230 actually affecting hardware. Often the 230 actually affecting hardware. Often the information is needed when 231 the user can change controls by keyboa 231 the user can change controls by keyboard or GUI buttons, rather 232 than a slider. When for example a hard 232 than a slider. When for example a hardware register accepts values 233 0-511 and the driver reports 0-65535, 233 0-511 and the driver reports 0-65535, step should be 128. 234 * - __s64 234 * - __s64 235 - ``default_value`` 235 - ``default_value`` 236 - The default value of a ``V4L2_CTRL_TYP 236 - The default value of a ``V4L2_CTRL_TYPE_INTEGER``, ``_INTEGER64``, 237 ``_BOOLEAN``, ``_BITMASK``, ``_MENU``, 237 ``_BOOLEAN``, ``_BITMASK``, ``_MENU``, ``_INTEGER_MENU``, ``_U8`` 238 or ``_U16`` control. Not valid for oth 238 or ``_U16`` control. Not valid for other types of controls. 239 239 240 .. note:: 240 .. note:: 241 241 242 Drivers reset controls to their def 242 Drivers reset controls to their default value only when 243 the driver is first loaded, never a 243 the driver is first loaded, never afterwards. 244 * - __u32 244 * - __u32 245 - ``flags`` 245 - ``flags`` 246 - Control flags, see :ref:`control-flags 246 - Control flags, see :ref:`control-flags`. 247 * - __u32 247 * - __u32 248 - ``elem_size`` 248 - ``elem_size`` 249 - The size in bytes of a single element 249 - The size in bytes of a single element of the array. Given a char 250 pointer ``p`` to a 3-dimensional array 250 pointer ``p`` to a 3-dimensional array you can find the position 251 of cell ``(z, y, x)`` as follows: 251 of cell ``(z, y, x)`` as follows: 252 ``p + ((z * dims[1] + y) * dims[0] + x 252 ``p + ((z * dims[1] + y) * dims[0] + x) * elem_size``. 253 ``elem_size`` is always valid, also wh 253 ``elem_size`` is always valid, also when the control isn't an 254 array. For string controls ``elem_size 254 array. For string controls ``elem_size`` is equal to 255 ``maximum + 1``. 255 ``maximum + 1``. 256 * - __u32 256 * - __u32 257 - ``elems`` 257 - ``elems`` 258 - The number of elements in the N-dimens 258 - The number of elements in the N-dimensional array. If this control 259 is not an array, then ``elems`` is 1. 259 is not an array, then ``elems`` is 1. The ``elems`` field can 260 never be 0. 260 never be 0. 261 * - __u32 261 * - __u32 262 - ``nr_of_dims`` 262 - ``nr_of_dims`` 263 - The number of dimension in the N-dimen 263 - The number of dimension in the N-dimensional array. If this 264 control is not an array, then this fie 264 control is not an array, then this field is 0. 265 * - __u32 265 * - __u32 266 - ``dims[V4L2_CTRL_MAX_DIMS]`` 266 - ``dims[V4L2_CTRL_MAX_DIMS]`` 267 - The size of each dimension. The first 267 - The size of each dimension. The first ``nr_of_dims`` elements of 268 this array must be non-zero, all remai 268 this array must be non-zero, all remaining elements must be zero. 269 * - __u32 269 * - __u32 270 - ``reserved``\ [32] 270 - ``reserved``\ [32] 271 - Reserved for future extensions. Applic 271 - Reserved for future extensions. Applications and drivers must set 272 the array to zero. 272 the array to zero. 273 273 274 274 275 .. tabularcolumns:: |p{1.2cm}|p{3.0cm}|p{13.1c 275 .. tabularcolumns:: |p{1.2cm}|p{3.0cm}|p{13.1cm}| 276 276 277 .. _v4l2-querymenu: 277 .. _v4l2-querymenu: 278 278 279 .. flat-table:: struct v4l2_querymenu 279 .. flat-table:: struct v4l2_querymenu 280 :header-rows: 0 280 :header-rows: 0 281 :stub-columns: 0 281 :stub-columns: 0 282 :widths: 1 1 2 282 :widths: 1 1 2 283 283 284 * - __u32 284 * - __u32 285 - ``id`` 285 - ``id`` 286 - Identifies the control, set by the app 286 - Identifies the control, set by the application from the respective 287 struct :ref:`v4l2_queryctrl <v4l2-quer 287 struct :ref:`v4l2_queryctrl <v4l2-queryctrl>` ``id``. 288 * - __u32 288 * - __u32 289 - ``index`` 289 - ``index`` 290 - Index of the menu item, starting at ze 290 - Index of the menu item, starting at zero, set by the application. 291 * - union { 291 * - union { 292 - (anonymous) 292 - (anonymous) 293 * - __u8 293 * - __u8 294 - ``name``\ [32] 294 - ``name``\ [32] 295 - Name of the menu item, a NUL-terminate 295 - Name of the menu item, a NUL-terminated ASCII string. This 296 information is intended for the user. 296 information is intended for the user. This field is valid for 297 ``V4L2_CTRL_TYPE_MENU`` type controls. 297 ``V4L2_CTRL_TYPE_MENU`` type controls. 298 * - __s64 298 * - __s64 299 - ``value`` 299 - ``value`` 300 - Value of the integer menu item. This f 300 - Value of the integer menu item. This field is valid for 301 ``V4L2_CTRL_TYPE_INTEGER_MENU`` type c 301 ``V4L2_CTRL_TYPE_INTEGER_MENU`` type controls. 302 * - } 302 * - } 303 - 303 - 304 * - __u32 304 * - __u32 305 - ``reserved`` 305 - ``reserved`` 306 - Reserved for future extensions. Driver 306 - Reserved for future extensions. Drivers must set the array to 307 zero. 307 zero. 308 308 309 .. c:type:: v4l2_ctrl_type 309 .. c:type:: v4l2_ctrl_type 310 310 311 .. raw:: latex 311 .. raw:: latex 312 312 313 \footnotesize 313 \footnotesize 314 314 315 .. tabularcolumns:: |p{6.5cm}|p{1.5cm}|p{1.1cm 315 .. tabularcolumns:: |p{6.5cm}|p{1.5cm}|p{1.1cm}|p{1.5cm}|p{6.8cm}| 316 316 317 .. cssclass:: longtable 317 .. cssclass:: longtable 318 318 319 .. flat-table:: enum v4l2_ctrl_type 319 .. flat-table:: enum v4l2_ctrl_type 320 :header-rows: 1 320 :header-rows: 1 321 :stub-columns: 0 321 :stub-columns: 0 322 :widths: 30 5 5 5 55 322 :widths: 30 5 5 5 55 323 323 324 * - Type 324 * - Type 325 - ``minimum`` 325 - ``minimum`` 326 - ``step`` 326 - ``step`` 327 - ``maximum`` 327 - ``maximum`` 328 - Description 328 - Description 329 * - ``V4L2_CTRL_TYPE_INTEGER`` 329 * - ``V4L2_CTRL_TYPE_INTEGER`` 330 - any 330 - any 331 - any 331 - any 332 - any 332 - any 333 - An integer-valued control ranging from 333 - An integer-valued control ranging from minimum to maximum 334 inclusive. The step value indicates th 334 inclusive. The step value indicates the increment between values. 335 * - ``V4L2_CTRL_TYPE_BOOLEAN`` 335 * - ``V4L2_CTRL_TYPE_BOOLEAN`` 336 - 0 336 - 0 337 - 1 337 - 1 338 - 1 338 - 1 339 - A boolean-valued control. Zero corresp 339 - A boolean-valued control. Zero corresponds to "disabled", and one 340 means "enabled". 340 means "enabled". 341 * - ``V4L2_CTRL_TYPE_MENU`` 341 * - ``V4L2_CTRL_TYPE_MENU`` 342 - ≥ 0 342 - ≥ 0 343 - 1 343 - 1 344 - N-1 344 - N-1 345 - The control has a menu of N choices. T 345 - The control has a menu of N choices. The names of the menu items 346 can be enumerated with the ``VIDIOC_QU 346 can be enumerated with the ``VIDIOC_QUERYMENU`` ioctl. 347 * - ``V4L2_CTRL_TYPE_INTEGER_MENU`` 347 * - ``V4L2_CTRL_TYPE_INTEGER_MENU`` 348 - ≥ 0 348 - ≥ 0 349 - 1 349 - 1 350 - N-1 350 - N-1 351 - The control has a menu of N choices. T 351 - The control has a menu of N choices. The values of the menu items 352 can be enumerated with the ``VIDIOC_QU 352 can be enumerated with the ``VIDIOC_QUERYMENU`` ioctl. This is 353 similar to ``V4L2_CTRL_TYPE_MENU`` exc 353 similar to ``V4L2_CTRL_TYPE_MENU`` except that instead of strings, 354 the menu items are signed 64-bit integ 354 the menu items are signed 64-bit integers. 355 * - ``V4L2_CTRL_TYPE_BITMASK`` 355 * - ``V4L2_CTRL_TYPE_BITMASK`` 356 - 0 356 - 0 357 - n/a 357 - n/a 358 - any 358 - any 359 - A bitmask field. The maximum value is 359 - A bitmask field. The maximum value is the set of bits that can be 360 used, all other bits are to be 0. The 360 used, all other bits are to be 0. The maximum value is interpreted 361 as a __u32, allowing the use of bit 31 361 as a __u32, allowing the use of bit 31 in the bitmask. 362 * - ``V4L2_CTRL_TYPE_BUTTON`` 362 * - ``V4L2_CTRL_TYPE_BUTTON`` 363 - 0 363 - 0 364 - 0 364 - 0 365 - 0 365 - 0 366 - A control which performs an action whe 366 - A control which performs an action when set. Drivers must ignore 367 the value passed with ``VIDIOC_S_CTRL` 367 the value passed with ``VIDIOC_S_CTRL`` and return an ``EACCES`` error 368 code on a ``VIDIOC_G_CTRL`` attempt. 368 code on a ``VIDIOC_G_CTRL`` attempt. 369 * - ``V4L2_CTRL_TYPE_INTEGER64`` 369 * - ``V4L2_CTRL_TYPE_INTEGER64`` 370 - any 370 - any 371 - any 371 - any 372 - any 372 - any 373 - A 64-bit integer valued control. Minim 373 - A 64-bit integer valued control. Minimum, maximum and step size 374 cannot be queried using ``VIDIOC_QUERY 374 cannot be queried using ``VIDIOC_QUERYCTRL``. Only 375 ``VIDIOC_QUERY_EXT_CTRL`` can retrieve 375 ``VIDIOC_QUERY_EXT_CTRL`` can retrieve the 64-bit min/max/step 376 values, they should be interpreted as 376 values, they should be interpreted as n/a when using 377 ``VIDIOC_QUERYCTRL``. 377 ``VIDIOC_QUERYCTRL``. 378 * - ``V4L2_CTRL_TYPE_STRING`` 378 * - ``V4L2_CTRL_TYPE_STRING`` 379 - ≥ 0 379 - ≥ 0 380 - ≥ 1 380 - ≥ 1 381 - ≥ 0 381 - ≥ 0 382 - The minimum and maximum string lengths 382 - The minimum and maximum string lengths. The step size means that 383 the string must be (minimum + N * step 383 the string must be (minimum + N * step) characters long for N ≥ 0. 384 These lengths do not include the termi 384 These lengths do not include the terminating zero, so in order to 385 pass a string of length 8 to 385 pass a string of length 8 to 386 :ref:`VIDIOC_S_EXT_CTRLS <VIDIOC_G_EXT 386 :ref:`VIDIOC_S_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>` you need to 387 set the ``size`` field of struct 387 set the ``size`` field of struct 388 :c:type:`v4l2_ext_control` to 9. For 388 :c:type:`v4l2_ext_control` to 9. For 389 :ref:`VIDIOC_G_EXT_CTRLS <VIDIOC_G_EXT 389 :ref:`VIDIOC_G_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>` you can set 390 the ``size`` field to ``maximum`` + 1. 390 the ``size`` field to ``maximum`` + 1. Which character encoding is 391 used will depend on the string control 391 used will depend on the string control itself and should be part 392 of the control documentation. 392 of the control documentation. 393 * - ``V4L2_CTRL_TYPE_CTRL_CLASS`` 393 * - ``V4L2_CTRL_TYPE_CTRL_CLASS`` 394 - n/a 394 - n/a 395 - n/a 395 - n/a 396 - n/a 396 - n/a 397 - This is not a control. When ``VIDIOC_Q 397 - This is not a control. When ``VIDIOC_QUERYCTRL`` is called with a 398 control ID equal to a control class co 398 control ID equal to a control class code (see :ref:`ctrl-class`) 399 + 1, the ioctl returns the name of the 399 + 1, the ioctl returns the name of the control class and this 400 control type. Older drivers which do n 400 control type. Older drivers which do not support this feature 401 return an ``EINVAL`` error code. 401 return an ``EINVAL`` error code. 402 * - ``V4L2_CTRL_TYPE_U8`` 402 * - ``V4L2_CTRL_TYPE_U8`` 403 - any 403 - any 404 - any 404 - any 405 - any 405 - any 406 - An unsigned 8-bit valued control rangi 406 - An unsigned 8-bit valued control ranging from minimum to maximum 407 inclusive. The step value indicates th 407 inclusive. The step value indicates the increment between values. 408 * - ``V4L2_CTRL_TYPE_U16`` 408 * - ``V4L2_CTRL_TYPE_U16`` 409 - any 409 - any 410 - any 410 - any 411 - any 411 - any 412 - An unsigned 16-bit valued control rang 412 - An unsigned 16-bit valued control ranging from minimum to maximum 413 inclusive. The step value indicates th 413 inclusive. The step value indicates the increment between values. 414 * - ``V4L2_CTRL_TYPE_U32`` 414 * - ``V4L2_CTRL_TYPE_U32`` 415 - any 415 - any 416 - any 416 - any 417 - any 417 - any 418 - An unsigned 32-bit valued control rang 418 - An unsigned 32-bit valued control ranging from minimum to maximum 419 inclusive. The step value indicates th 419 inclusive. The step value indicates the increment between values. 420 * - ``V4L2_CTRL_TYPE_MPEG2_QUANTISATION`` 420 * - ``V4L2_CTRL_TYPE_MPEG2_QUANTISATION`` 421 - n/a 421 - n/a 422 - n/a 422 - n/a 423 - n/a 423 - n/a 424 - A struct :c:type:`v4l2_ctrl_mpeg2_quan 424 - A struct :c:type:`v4l2_ctrl_mpeg2_quantisation`, containing MPEG-2 425 quantisation matrices for stateless vi 425 quantisation matrices for stateless video decoders. 426 * - ``V4L2_CTRL_TYPE_MPEG2_SEQUENCE`` 426 * - ``V4L2_CTRL_TYPE_MPEG2_SEQUENCE`` 427 - n/a 427 - n/a 428 - n/a 428 - n/a 429 - n/a 429 - n/a 430 - A struct :c:type:`v4l2_ctrl_mpeg2_sequ 430 - A struct :c:type:`v4l2_ctrl_mpeg2_sequence`, containing MPEG-2 431 sequence parameters for stateless vide 431 sequence parameters for stateless video decoders. 432 * - ``V4L2_CTRL_TYPE_MPEG2_PICTURE`` 432 * - ``V4L2_CTRL_TYPE_MPEG2_PICTURE`` 433 - n/a 433 - n/a 434 - n/a 434 - n/a 435 - n/a 435 - n/a 436 - A struct :c:type:`v4l2_ctrl_mpeg2_pict 436 - A struct :c:type:`v4l2_ctrl_mpeg2_picture`, containing MPEG-2 437 picture parameters for stateless video 437 picture parameters for stateless video decoders. 438 * - ``V4L2_CTRL_TYPE_AREA`` 438 * - ``V4L2_CTRL_TYPE_AREA`` 439 - n/a 439 - n/a 440 - n/a 440 - n/a 441 - n/a 441 - n/a 442 - A struct :c:type:`v4l2_area`, containi 442 - A struct :c:type:`v4l2_area`, containing the width and the height 443 of a rectangular area. Units depend on 443 of a rectangular area. Units depend on the use case. 444 * - ``V4L2_CTRL_TYPE_H264_SPS`` 444 * - ``V4L2_CTRL_TYPE_H264_SPS`` 445 - n/a 445 - n/a 446 - n/a 446 - n/a 447 - n/a 447 - n/a 448 - A struct :c:type:`v4l2_ctrl_h264_sps`, 448 - A struct :c:type:`v4l2_ctrl_h264_sps`, containing H264 449 sequence parameters for stateless vide 449 sequence parameters for stateless video decoders. 450 * - ``V4L2_CTRL_TYPE_H264_PPS`` 450 * - ``V4L2_CTRL_TYPE_H264_PPS`` 451 - n/a 451 - n/a 452 - n/a 452 - n/a 453 - n/a 453 - n/a 454 - A struct :c:type:`v4l2_ctrl_h264_pps`, 454 - A struct :c:type:`v4l2_ctrl_h264_pps`, containing H264 455 picture parameters for stateless video 455 picture parameters for stateless video decoders. 456 * - ``V4L2_CTRL_TYPE_H264_SCALING_MATRIX`` 456 * - ``V4L2_CTRL_TYPE_H264_SCALING_MATRIX`` 457 - n/a 457 - n/a 458 - n/a 458 - n/a 459 - n/a 459 - n/a 460 - A struct :c:type:`v4l2_ctrl_h264_scali 460 - A struct :c:type:`v4l2_ctrl_h264_scaling_matrix`, containing H264 461 scaling matrices for stateless video d 461 scaling matrices for stateless video decoders. 462 * - ``V4L2_CTRL_TYPE_H264_SLICE_PARAMS`` 462 * - ``V4L2_CTRL_TYPE_H264_SLICE_PARAMS`` 463 - n/a 463 - n/a 464 - n/a 464 - n/a 465 - n/a 465 - n/a 466 - A struct :c:type:`v4l2_ctrl_h264_slice 466 - A struct :c:type:`v4l2_ctrl_h264_slice_params`, containing H264 467 slice parameters for stateless video d 467 slice parameters for stateless video decoders. 468 * - ``V4L2_CTRL_TYPE_H264_DECODE_PARAMS`` 468 * - ``V4L2_CTRL_TYPE_H264_DECODE_PARAMS`` 469 - n/a 469 - n/a 470 - n/a 470 - n/a 471 - n/a 471 - n/a 472 - A struct :c:type:`v4l2_ctrl_h264_decod 472 - A struct :c:type:`v4l2_ctrl_h264_decode_params`, containing H264 473 decode parameters for stateless video 473 decode parameters for stateless video decoders. 474 * - ``V4L2_CTRL_TYPE_FWHT_PARAMS`` 474 * - ``V4L2_CTRL_TYPE_FWHT_PARAMS`` 475 - n/a 475 - n/a 476 - n/a 476 - n/a 477 - n/a 477 - n/a 478 - A struct :c:type:`v4l2_ctrl_fwht_param 478 - A struct :c:type:`v4l2_ctrl_fwht_params`, containing FWHT 479 parameters for stateless video decoder 479 parameters for stateless video decoders. 480 * - ``V4L2_CTRL_TYPE_HEVC_SPS`` 480 * - ``V4L2_CTRL_TYPE_HEVC_SPS`` 481 - n/a 481 - n/a 482 - n/a 482 - n/a 483 - n/a 483 - n/a 484 - A struct :c:type:`v4l2_ctrl_hevc_sps`, 484 - A struct :c:type:`v4l2_ctrl_hevc_sps`, containing HEVC Sequence 485 Parameter Set for stateless video deco 485 Parameter Set for stateless video decoders. 486 * - ``V4L2_CTRL_TYPE_HEVC_PPS`` 486 * - ``V4L2_CTRL_TYPE_HEVC_PPS`` 487 - n/a 487 - n/a 488 - n/a 488 - n/a 489 - n/a 489 - n/a 490 - A struct :c:type:`v4l2_ctrl_hevc_pps`, 490 - A struct :c:type:`v4l2_ctrl_hevc_pps`, containing HEVC Picture 491 Parameter Set for stateless video deco 491 Parameter Set for stateless video decoders. 492 * - ``V4L2_CTRL_TYPE_HEVC_SLICE_PARAMS`` 492 * - ``V4L2_CTRL_TYPE_HEVC_SLICE_PARAMS`` 493 - n/a 493 - n/a 494 - n/a 494 - n/a 495 - n/a 495 - n/a 496 - A struct :c:type:`v4l2_ctrl_hevc_slice 496 - A struct :c:type:`v4l2_ctrl_hevc_slice_params`, containing HEVC 497 slice parameters for stateless video d 497 slice parameters for stateless video decoders. 498 * - ``V4L2_CTRL_TYPE_HEVC_SCALING_MATRIX`` << 499 - n/a << 500 - n/a << 501 - n/a << 502 - A struct :c:type:`v4l2_ctrl_hevc_scali << 503 scaling matrix for stateless video dec << 504 * - ``V4L2_CTRL_TYPE_VP8_FRAME`` 498 * - ``V4L2_CTRL_TYPE_VP8_FRAME`` 505 - n/a 499 - n/a 506 - n/a 500 - n/a 507 - n/a 501 - n/a 508 - A struct :c:type:`v4l2_ctrl_vp8_frame` 502 - A struct :c:type:`v4l2_ctrl_vp8_frame`, containing VP8 509 frame parameters for stateless video d 503 frame parameters for stateless video decoders. 510 * - ``V4L2_CTRL_TYPE_HEVC_DECODE_PARAMS`` 504 * - ``V4L2_CTRL_TYPE_HEVC_DECODE_PARAMS`` 511 - n/a 505 - n/a 512 - n/a 506 - n/a 513 - n/a 507 - n/a 514 - A struct :c:type:`v4l2_ctrl_hevc_decod 508 - A struct :c:type:`v4l2_ctrl_hevc_decode_params`, containing HEVC 515 decoding parameters for stateless vide 509 decoding parameters for stateless video decoders. 516 * - ``V4L2_CTRL_TYPE_VP9_COMPRESSED_HDR`` << 517 - n/a << 518 - n/a << 519 - n/a << 520 - A struct :c:type:`v4l2_ctrl_vp9_compre << 521 probabilities updates for stateless vi << 522 * - ``V4L2_CTRL_TYPE_VP9_FRAME`` << 523 - n/a << 524 - n/a << 525 - n/a << 526 - A struct :c:type:`v4l2_ctrl_vp9_frame` << 527 frame decode parameters for stateless << 528 * - ``V4L2_CTRL_TYPE_AV1_SEQUENCE`` << 529 - n/a << 530 - n/a << 531 - n/a << 532 - A struct :c:type:`v4l2_ctrl_av1_sequen << 533 decoding parameters for stateless vide << 534 * - ``V4L2_CTRL_TYPE_AV1_TILE_GROUP_ENTRY` << 535 - n/a << 536 - n/a << 537 - n/a << 538 - A struct :c:type:`v4l2_ctrl_av1_tile_g << 539 OBU decoding parameters for stateless << 540 * - ``V4L2_CTRL_TYPE_AV1_FRAME`` << 541 - n/a << 542 - n/a << 543 - n/a << 544 - A struct :c:type:`v4l2_ctrl_av1_frame` << 545 Header OBU decoding parameters for sta << 546 * - ``V4L2_CTRL_TYPE_AV1_FILM_GRAIN`` << 547 - n/a << 548 - n/a << 549 - n/a << 550 - A struct :c:type:`v4l2_ctrl_av1_film_g << 551 parameters for stateless video decoder << 552 510 553 .. raw:: latex 511 .. raw:: latex 554 512 555 \normalsize 513 \normalsize 556 514 557 .. tabularcolumns:: |p{7.3cm}|p{1.8cm}|p{8.2cm 515 .. tabularcolumns:: |p{7.3cm}|p{1.8cm}|p{8.2cm}| 558 516 559 .. cssclass:: longtable 517 .. cssclass:: longtable 560 518 561 .. _control-flags: 519 .. _control-flags: 562 520 563 .. flat-table:: Control Flags 521 .. flat-table:: Control Flags 564 :header-rows: 0 522 :header-rows: 0 565 :stub-columns: 0 523 :stub-columns: 0 566 :widths: 3 1 4 524 :widths: 3 1 4 567 525 568 * - ``V4L2_CTRL_FLAG_DISABLED`` 526 * - ``V4L2_CTRL_FLAG_DISABLED`` 569 - 0x0001 527 - 0x0001 570 - This control is permanently disabled a 528 - This control is permanently disabled and should be ignored by the 571 application. Any attempt to change the 529 application. Any attempt to change the control will result in an 572 ``EINVAL`` error code. 530 ``EINVAL`` error code. 573 * - ``V4L2_CTRL_FLAG_GRABBED`` 531 * - ``V4L2_CTRL_FLAG_GRABBED`` 574 - 0x0002 532 - 0x0002 575 - This control is temporarily unchangeab 533 - This control is temporarily unchangeable, for example because 576 another application took over control 534 another application took over control of the respective resource. 577 Such controls may be displayed special 535 Such controls may be displayed specially in a user interface. 578 Attempts to change the control may res 536 Attempts to change the control may result in an ``EBUSY`` error code. 579 * - ``V4L2_CTRL_FLAG_READ_ONLY`` 537 * - ``V4L2_CTRL_FLAG_READ_ONLY`` 580 - 0x0004 538 - 0x0004 581 - This control is permanently readable o 539 - This control is permanently readable only. Any attempt to change 582 the control will result in an ``EINVAL 540 the control will result in an ``EINVAL`` error code. 583 * - ``V4L2_CTRL_FLAG_UPDATE`` 541 * - ``V4L2_CTRL_FLAG_UPDATE`` 584 - 0x0008 542 - 0x0008 585 - A hint that changing this control may 543 - A hint that changing this control may affect the value of other 586 controls within the same control class 544 controls within the same control class. Applications should update 587 their user interface accordingly. 545 their user interface accordingly. 588 * - ``V4L2_CTRL_FLAG_INACTIVE`` 546 * - ``V4L2_CTRL_FLAG_INACTIVE`` 589 - 0x0010 547 - 0x0010 590 - This control is not applicable to the 548 - This control is not applicable to the current configuration and 591 should be displayed accordingly in a u 549 should be displayed accordingly in a user interface. For example 592 the flag may be set on a MPEG audio le 550 the flag may be set on a MPEG audio level 2 bitrate control when 593 MPEG audio encoding level 1 was select 551 MPEG audio encoding level 1 was selected with another control. 594 * - ``V4L2_CTRL_FLAG_SLIDER`` 552 * - ``V4L2_CTRL_FLAG_SLIDER`` 595 - 0x0020 553 - 0x0020 596 - A hint that this control is best repre 554 - A hint that this control is best represented as a slider-like 597 element in a user interface. 555 element in a user interface. 598 * - ``V4L2_CTRL_FLAG_WRITE_ONLY`` 556 * - ``V4L2_CTRL_FLAG_WRITE_ONLY`` 599 - 0x0040 557 - 0x0040 600 - This control is permanently writable o 558 - This control is permanently writable only. Any attempt to read the 601 control will result in an ``EACCES`` e 559 control will result in an ``EACCES`` error code error code. This flag 602 is typically present for relative cont 560 is typically present for relative controls or action controls 603 where writing a value will cause the d 561 where writing a value will cause the device to carry out a given 604 action (e. g. motor control) but no me 562 action (e. g. motor control) but no meaningful value can be 605 returned. 563 returned. 606 * - ``V4L2_CTRL_FLAG_VOLATILE`` 564 * - ``V4L2_CTRL_FLAG_VOLATILE`` 607 - 0x0080 565 - 0x0080 608 - This control is volatile, which means 566 - This control is volatile, which means that the value of the 609 control changes continuously. A typica 567 control changes continuously. A typical example would be the 610 current gain value if the device is in 568 current gain value if the device is in auto-gain mode. In such a 611 case the hardware calculates the gain 569 case the hardware calculates the gain value based on the lighting 612 conditions which can change over time. 570 conditions which can change over time. 613 571 614 .. note:: 572 .. note:: 615 573 616 Setting a new value for a volatile 574 Setting a new value for a volatile control will be ignored 617 unless 575 unless 618 :ref:`V4L2_CTRL_FLAG_EXECUTE_ON_WRI 576 :ref:`V4L2_CTRL_FLAG_EXECUTE_ON_WRITE <FLAG_EXECUTE_ON_WRITE>` 619 is also set. 577 is also set. 620 Setting a new value for a volatile 578 Setting a new value for a volatile control will *never* trigger a 621 :ref:`V4L2_EVENT_CTRL_CH_VALUE <ctr 579 :ref:`V4L2_EVENT_CTRL_CH_VALUE <ctrl-changes-flags>` event. 622 * - ``V4L2_CTRL_FLAG_HAS_PAYLOAD`` 580 * - ``V4L2_CTRL_FLAG_HAS_PAYLOAD`` 623 - 0x0100 581 - 0x0100 624 - This control has a pointer type, so it 582 - This control has a pointer type, so its value has to be accessed 625 using one of the pointer fields of str 583 using one of the pointer fields of struct 626 :c:type:`v4l2_ext_control`. This flag 584 :c:type:`v4l2_ext_control`. This flag is set 627 for controls that are an array, string 585 for controls that are an array, string, or have a compound type. 628 In all cases you have to set a pointer 586 In all cases you have to set a pointer to memory containing the 629 payload of the control. 587 payload of the control. 630 * .. _FLAG_EXECUTE_ON_WRITE: 588 * .. _FLAG_EXECUTE_ON_WRITE: 631 589 632 - ``V4L2_CTRL_FLAG_EXECUTE_ON_WRITE`` 590 - ``V4L2_CTRL_FLAG_EXECUTE_ON_WRITE`` 633 - 0x0200 591 - 0x0200 634 - The value provided to the control will 592 - The value provided to the control will be propagated to the driver 635 even if it remains constant. This is r 593 even if it remains constant. This is required when the control 636 represents an action on the hardware. 594 represents an action on the hardware. For example: clearing an 637 error flag or triggering the flash. Al 595 error flag or triggering the flash. All the controls of the type 638 ``V4L2_CTRL_TYPE_BUTTON`` have this fl 596 ``V4L2_CTRL_TYPE_BUTTON`` have this flag set. 639 * .. _FLAG_MODIFY_LAYOUT: 597 * .. _FLAG_MODIFY_LAYOUT: 640 598 641 - ``V4L2_CTRL_FLAG_MODIFY_LAYOUT`` 599 - ``V4L2_CTRL_FLAG_MODIFY_LAYOUT`` 642 - 0x0400 600 - 0x0400 643 - Changing this control value may modify 601 - Changing this control value may modify the layout of the 644 buffer (for video devices) or the medi 602 buffer (for video devices) or the media bus format (for sub-devices). 645 603 646 A typical example would be the ``V4L2_ 604 A typical example would be the ``V4L2_CID_ROTATE`` control. 647 605 648 Note that typically controls with this 606 Note that typically controls with this flag will also set the 649 ``V4L2_CTRL_FLAG_GRABBED`` flag when b 607 ``V4L2_CTRL_FLAG_GRABBED`` flag when buffers are allocated or 650 streaming is in progress since most dr 608 streaming is in progress since most drivers do not support changing 651 the format in that case. 609 the format in that case. 652 * - ``V4L2_CTRL_FLAG_DYNAMIC_ARRAY`` << 653 - 0x0800 << 654 - This control is a dynamically sized 1- << 655 behaves the same as a regular array, e << 656 of elements as reported by the ``elems << 657 ``dims[0]``. So setting the control wi << 658 array will change the ``elems`` field << 659 queried afterwards. << 660 610 661 Return Value 611 Return Value 662 ============ 612 ============ 663 613 664 On success 0 is returned, on error -1 and the 614 On success 0 is returned, on error -1 and the ``errno`` variable is set 665 appropriately. The generic error codes are des 615 appropriately. The generic error codes are described at the 666 :ref:`Generic Error Codes <gen-errors>` chapte 616 :ref:`Generic Error Codes <gen-errors>` chapter. 667 617 668 EINVAL 618 EINVAL 669 The struct :ref:`v4l2_queryctrl <v4l2-quer 619 The struct :ref:`v4l2_queryctrl <v4l2-queryctrl>` ``id`` is 670 invalid. The struct :ref:`v4l2_querymenu < 620 invalid. The struct :ref:`v4l2_querymenu <v4l2-querymenu>` ``id`` 671 is invalid or ``index`` is out of range (l 621 is invalid or ``index`` is out of range (less than ``minimum`` or 672 greater than ``maximum``) or this particul 622 greater than ``maximum``) or this particular menu item is not 673 supported by the driver. 623 supported by the driver. 674 624 675 EACCES 625 EACCES 676 An attempt was made to read a write-only c 626 An attempt was made to read a write-only control. 677 627 678 .. [#f1] 628 .. [#f1] 679 ``V4L2_CTRL_FLAG_DISABLED`` was intended fo 629 ``V4L2_CTRL_FLAG_DISABLED`` was intended for two purposes: Drivers 680 can skip predefined controls not supported 630 can skip predefined controls not supported by the hardware (although 681 returning ``EINVAL`` would do as well), or 631 returning ``EINVAL`` would do as well), or disable predefined and private 682 controls after hardware detection without t 632 controls after hardware detection without the trouble of reordering 683 control arrays and indices (``EINVAL`` cann 633 control arrays and indices (``EINVAL`` cannot be used to skip private 684 controls because it would prematurely end t 634 controls because it would prematurely end the enumeration).
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