1.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later 2.. c:namespace:: V4L 3 4.. _VIDIOC_G_EXT_CTRLS: 5 6****************************************************************** 7ioctl VIDIOC_G_EXT_CTRLS, VIDIOC_S_EXT_CTRLS, VIDIOC_TRY_EXT_CTRLS 8****************************************************************** 9 10Name 11==== 12 13VIDIOC_G_EXT_CTRLS - VIDIOC_S_EXT_CTRLS - VIDIOC_TRY_EXT_CTRLS - Get or set the value of several controls, try control values 14 15Synopsis 16======== 17 18.. c:macro:: VIDIOC_G_EXT_CTRLS 19 20``int ioctl(int fd, VIDIOC_G_EXT_CTRLS, struct v4l2_ext_controls *argp)`` 21 22.. c:macro:: VIDIOC_S_EXT_CTRLS 23 24``int ioctl(int fd, VIDIOC_S_EXT_CTRLS, struct v4l2_ext_controls *argp)`` 25 26.. c:macro:: VIDIOC_TRY_EXT_CTRLS 27 28``int ioctl(int fd, VIDIOC_TRY_EXT_CTRLS, struct v4l2_ext_controls *argp)`` 29 30Arguments 31========= 32 33``fd`` 34 File descriptor returned by :c:func:`open()`. 35 36``argp`` 37 Pointer to struct :c:type:`v4l2_ext_controls`. 38 39Description 40=========== 41 42These ioctls allow the caller to get or set multiple controls 43atomically. Control IDs are grouped into control classes (see 44:ref:`ctrl-class`) and all controls in the control array must belong 45to the same control class. 46 47Applications must always fill in the ``count``, ``which``, ``controls`` 48and ``reserved`` fields of struct 49:c:type:`v4l2_ext_controls`, and initialize the 50struct :c:type:`v4l2_ext_control` array pointed to 51by the ``controls`` fields. 52 53To get the current value of a set of controls applications initialize 54the ``id``, ``size`` and ``reserved2`` fields of each struct 55:c:type:`v4l2_ext_control` and call the 56:ref:`VIDIOC_G_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>` ioctl. String controls must also set the 57``string`` field. Controls of compound types 58(``V4L2_CTRL_FLAG_HAS_PAYLOAD`` is set) must set the ``ptr`` field. 59 60If the ``size`` is too small to receive the control result (only 61relevant for pointer-type controls like strings), then the driver will 62set ``size`` to a valid value and return an ``ENOSPC`` error code. You 63should re-allocate the memory to this new size and try again. For the 64string type it is possible that the same issue occurs again if the 65string has grown in the meantime. It is recommended to call 66:ref:`VIDIOC_QUERYCTRL` first and use 67``maximum``\ +1 as the new ``size`` value. It is guaranteed that that is 68sufficient memory. 69 70N-dimensional arrays are set and retrieved row-by-row. You cannot set a 71partial array, all elements have to be set or retrieved. The total size 72is calculated as ``elems`` * ``elem_size``. These values can be obtained 73by calling :ref:`VIDIOC_QUERY_EXT_CTRL <VIDIOC_QUERYCTRL>`. 74 75To change the value of a set of controls applications initialize the 76``id``, ``size``, ``reserved2`` and ``value/value64/string/ptr`` fields 77of each struct :c:type:`v4l2_ext_control` and call 78the :ref:`VIDIOC_S_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>` ioctl. The controls will only be set if *all* 79control values are valid. 80 81To check if a set of controls have correct values applications 82initialize the ``id``, ``size``, ``reserved2`` and 83``value/value64/string/ptr`` fields of each struct 84:c:type:`v4l2_ext_control` and call the 85:ref:`VIDIOC_TRY_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>` ioctl. It is up to the driver whether wrong 86values are automatically adjusted to a valid value or if an error is 87returned. 88 89When the ``id`` or ``which`` is invalid drivers return an ``EINVAL`` error 90code. When the value is out of bounds drivers can choose to take the 91closest valid value or return an ``ERANGE`` error code, whatever seems more 92appropriate. In the first case the new value is set in struct 93:c:type:`v4l2_ext_control`. If the new control value 94is inappropriate (e.g. the given menu index is not supported by the menu 95control), then this will also result in an ``EINVAL`` error code error. 96 97If ``request_fd`` is set to a not-yet-queued :ref:`request <media-request-api>` 98file descriptor and ``which`` is set to ``V4L2_CTRL_WHICH_REQUEST_VAL``, 99then the controls are not applied immediately when calling 100:ref:`VIDIOC_S_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>`, but instead are applied by 101the driver for the buffer associated with the same request. 102If the device does not support requests, then ``EACCES`` will be returned. 103If requests are supported but an invalid request file descriptor is given, 104then ``EINVAL`` will be returned. 105 106An attempt to call :ref:`VIDIOC_S_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>` for a 107request that has already been queued will result in an ``EBUSY`` error. 108 109If ``request_fd`` is specified and ``which`` is set to 110``V4L2_CTRL_WHICH_REQUEST_VAL`` during a call to 111:ref:`VIDIOC_G_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>`, then it will return the 112values of the controls at the time of request completion. 113If the request is not yet completed, then this will result in an 114``EACCES`` error. 115 116The driver will only set/get these controls if all control values are 117correct. This prevents the situation where only some of the controls 118were set/get. Only low-level errors (e. g. a failed i2c command) can 119still cause this situation. 120 121.. tabularcolumns:: |p{6.8cm}|p{4.0cm}|p{6.5cm}| 122 123.. c:type:: v4l2_ext_control 124 125.. raw:: latex 126 127 \footnotesize 128 129.. cssclass:: longtable 130 131.. flat-table:: struct v4l2_ext_control 132 :header-rows: 0 133 :stub-columns: 0 134 :widths: 1 1 2 135 136 * - __u32 137 - ``id`` 138 - Identifies the control, set by the application. 139 * - __u32 140 - ``size`` 141 - The total size in bytes of the payload of this control. 142 * - :cspan:`2` The ``size`` field is normally 0, but for pointer 143 controls this should be set to the size of the memory that contains 144 the payload or that will receive the payload. 145 If :ref:`VIDIOC_G_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>` finds that this value 146 is less than is required to store the payload result, then it is set 147 to a value large enough to store the payload result and ``ENOSPC`` is 148 returned. 149 150 .. note:: 151 152 For string controls, this ``size`` field should 153 not be confused with the length of the string. This field refers 154 to the size of the memory that contains the string. The actual 155 *length* of the string may well be much smaller. 156 * - __u32 157 - ``reserved2``\ [1] 158 - Reserved for future extensions. Drivers and applications must set 159 the array to zero. 160 * - union { 161 - (anonymous) 162 * - __s32 163 - ``value`` 164 - New value or current value. Valid if this control is not of type 165 ``V4L2_CTRL_TYPE_INTEGER64`` and ``V4L2_CTRL_FLAG_HAS_PAYLOAD`` is 166 not set. 167 * - __s64 168 - ``value64`` 169 - New value or current value. Valid if this control is of type 170 ``V4L2_CTRL_TYPE_INTEGER64`` and ``V4L2_CTRL_FLAG_HAS_PAYLOAD`` is 171 not set. 172 * - char * 173 - ``string`` 174 - A pointer to a string. Valid if this control is of type 175 ``V4L2_CTRL_TYPE_STRING``. 176 * - __u8 * 177 - ``p_u8`` 178 - A pointer to a matrix control of unsigned 8-bit values. Valid if 179 this control is of type ``V4L2_CTRL_TYPE_U8``. 180 * - __u16 * 181 - ``p_u16`` 182 - A pointer to a matrix control of unsigned 16-bit values. Valid if 183 this control is of type ``V4L2_CTRL_TYPE_U16``. 184 * - __u32 * 185 - ``p_u32`` 186 - A pointer to a matrix control of unsigned 32-bit values. Valid if 187 this control is of type ``V4L2_CTRL_TYPE_U32``. 188 * - __s32 * 189 - ``p_s32`` 190 - A pointer to a matrix control of signed 32-bit values. Valid if 191 this control is of type ``V4L2_CTRL_TYPE_INTEGER`` and 192 ``V4L2_CTRL_FLAG_HAS_PAYLOAD`` is set. 193 * - __s64 * 194 - ``p_s64`` 195 - A pointer to a matrix control of signed 64-bit values. Valid if 196 this control is of type ``V4L2_CTRL_TYPE_INTEGER64`` and 197 ``V4L2_CTRL_FLAG_HAS_PAYLOAD`` is set. 198 * - struct :c:type:`v4l2_area` * 199 - ``p_area`` 200 - A pointer to a struct :c:type:`v4l2_area`. Valid if this control is 201 of type ``V4L2_CTRL_TYPE_AREA``. 202 * - struct :c:type:`v4l2_ctrl_h264_sps` * 203 - ``p_h264_sps`` 204 - A pointer to a struct :c:type:`v4l2_ctrl_h264_sps`. Valid if this control is 205 of type ``V4L2_CTRL_TYPE_H264_SPS``. 206 * - struct :c:type:`v4l2_ctrl_h264_pps` * 207 - ``p_h264_pps`` 208 - A pointer to a struct :c:type:`v4l2_ctrl_h264_pps`. Valid if this control is 209 of type ``V4L2_CTRL_TYPE_H264_PPS``. 210 * - struct :c:type:`v4l2_ctrl_h264_scaling_matrix` * 211 - ``p_h264_scaling_matrix`` 212 - A pointer to a struct :c:type:`v4l2_ctrl_h264_scaling_matrix`. Valid if this control is 213 of type ``V4L2_CTRL_TYPE_H264_SCALING_MATRIX``. 214 * - struct :c:type:`v4l2_ctrl_h264_pred_weights` * 215 - ``p_h264_pred_weights`` 216 - A pointer to a struct :c:type:`v4l2_ctrl_h264_pred_weights`. Valid if this control is 217 of type ``V4L2_CTRL_TYPE_H264_PRED_WEIGHTS``. 218 * - struct :c:type:`v4l2_ctrl_h264_slice_params` * 219 - ``p_h264_slice_params`` 220 - A pointer to a struct :c:type:`v4l2_ctrl_h264_slice_params`. Valid if this control is 221 of type ``V4L2_CTRL_TYPE_H264_SLICE_PARAMS``. 222 * - struct :c:type:`v4l2_ctrl_h264_decode_params` * 223 - ``p_h264_decode_params`` 224 - A pointer to a struct :c:type:`v4l2_ctrl_h264_decode_params`. Valid if this control is 225 of type ``V4L2_CTRL_TYPE_H264_DECODE_PARAMS``. 226 * - struct :c:type:`v4l2_ctrl_fwht_params` * 227 - ``p_fwht_params`` 228 - A pointer to a struct :c:type:`v4l2_ctrl_fwht_params`. Valid if this control is 229 of type ``V4L2_CTRL_TYPE_FWHT_PARAMS``. 230 * - struct :c:type:`v4l2_ctrl_vp8_frame` * 231 - ``p_vp8_frame`` 232 - A pointer to a struct :c:type:`v4l2_ctrl_vp8_frame`. Valid if this control is 233 of type ``V4L2_CTRL_TYPE_VP8_FRAME``. 234 * - struct :c:type:`v4l2_ctrl_mpeg2_sequence` * 235 - ``p_mpeg2_sequence`` 236 - A pointer to a struct :c:type:`v4l2_ctrl_mpeg2_sequence`. Valid if this control is 237 of type ``V4L2_CTRL_TYPE_MPEG2_SEQUENCE``. 238 * - struct :c:type:`v4l2_ctrl_mpeg2_picture` * 239 - ``p_mpeg2_picture`` 240 - A pointer to a struct :c:type:`v4l2_ctrl_mpeg2_picture`. Valid if this control is 241 of type ``V4L2_CTRL_TYPE_MPEG2_PICTURE``. 242 * - struct :c:type:`v4l2_ctrl_mpeg2_quantisation` * 243 - ``p_mpeg2_quantisation`` 244 - A pointer to a struct :c:type:`v4l2_ctrl_mpeg2_quantisation`. Valid if this control is 245 of type ``V4L2_CTRL_TYPE_MPEG2_QUANTISATION``. 246 * - struct :c:type:`v4l2_ctrl_vp9_compressed_hdr` * 247 - ``p_vp9_compressed_hdr_probs`` 248 - A pointer to a struct :c:type:`v4l2_ctrl_vp9_compressed_hdr`. Valid if this 249 control is of type ``V4L2_CTRL_TYPE_VP9_COMPRESSED_HDR``. 250 * - struct :c:type:`v4l2_ctrl_vp9_frame` * 251 - ``p_vp9_frame`` 252 - A pointer to a struct :c:type:`v4l2_ctrl_vp9_frame`. Valid if this 253 control is of type ``V4L2_CTRL_TYPE_VP9_FRAME``. 254 * - struct :c:type:`v4l2_ctrl_hdr10_cll_info` * 255 - ``p_hdr10_cll`` 256 - A pointer to a struct :c:type:`v4l2_ctrl_hdr10_cll_info`. Valid if this control is 257 of type ``V4L2_CTRL_TYPE_HDR10_CLL_INFO``. 258 * - struct :c:type:`v4l2_ctrl_hdr10_mastering_display` * 259 - ``p_hdr10_mastering`` 260 - A pointer to a struct :c:type:`v4l2_ctrl_hdr10_mastering_display`. Valid if this control is 261 of type ``V4L2_CTRL_TYPE_HDR10_MASTERING_DISPLAY``. 262 * - struct :c:type:`v4l2_ctrl_hevc_sps` * 263 - ``p_hevc_sps`` 264 - A pointer to a struct :c:type:`v4l2_ctrl_hevc_sps`. Valid if this 265 control is of type ``V4L2_CTRL_TYPE_HEVC_SPS``. 266 * - struct :c:type:`v4l2_ctrl_hevc_pps` * 267 - ``p_hevc_pps`` 268 - A pointer to a struct :c:type:`v4l2_ctrl_hevc_pps`. Valid if this 269 control is of type ``V4L2_CTRL_TYPE_HEVC_PPS``. 270 * - struct :c:type:`v4l2_ctrl_hevc_slice_params` * 271 - ``p_hevc_slice_params`` 272 - A pointer to a struct :c:type:`v4l2_ctrl_hevc_slice_params`. Valid if this 273 control is of type ``V4L2_CTRL_TYPE_HEVC_SLICE_PARAMS``. 274 * - struct :c:type:`v4l2_ctrl_hevc_scaling_matrix` * 275 - ``p_hevc_scaling_matrix`` 276 - A pointer to a struct :c:type:`v4l2_ctrl_hevc_scaling_matrix`. Valid if this 277 control is of type ``V4L2_CTRL_TYPE_HEVC_SCALING_MATRIX``. 278 * - struct :c:type:`v4l2_ctrl_hevc_decode_params` * 279 - ``p_hevc_decode_params`` 280 - A pointer to a struct :c:type:`v4l2_ctrl_hevc_decode_params`. Valid if this 281 control is of type ``V4L2_CTRL_TYPE_HEVC_DECODE_PARAMS``. 282 * - struct :c:type:`v4l2_ctrl_av1_sequence` * 283 - ``p_av1_sequence`` 284 - A pointer to a struct :c:type:`v4l2_ctrl_av1_sequence`. Valid if this control is 285 of type ``V4L2_CTRL_TYPE_AV1_SEQUENCE``. 286 * - struct :c:type:`v4l2_ctrl_av1_tile_group_entry` * 287 - ``p_av1_tile_group_entry`` 288 - A pointer to a struct :c:type:`v4l2_ctrl_av1_tile_group_entry`. Valid if this control is 289 of type ``V4L2_CTRL_TYPE_AV1_TILE_GROUP_ENTRY``. 290 * - struct :c:type:`v4l2_ctrl_av1_frame` * 291 - ``p_av1_frame`` 292 - A pointer to a struct :c:type:`v4l2_ctrl_av1_frame`. Valid if this control is 293 of type ``V4L2_CTRL_TYPE_AV1_FRAME``. 294 * - struct :c:type:`v4l2_ctrl_av1_film_grain` * 295 - ``p_av1_film_grain`` 296 - A pointer to a struct :c:type:`v4l2_ctrl_av1_film_grain`. Valid if this control is 297 of type ``V4L2_CTRL_TYPE_AV1_FILM_GRAIN``. 298 * - void * 299 - ``ptr`` 300 - A pointer to a compound type which can be an N-dimensional array 301 and/or a compound type (the control's type is >= 302 ``V4L2_CTRL_COMPOUND_TYPES``). Valid if 303 ``V4L2_CTRL_FLAG_HAS_PAYLOAD`` is set for this control. 304 * - } 305 - 306 307.. raw:: latex 308 309 \normalsize 310 311.. tabularcolumns:: |p{4.0cm}|p{2.5cm}|p{10.8cm}| 312 313.. c:type:: v4l2_ext_controls 314 315.. cssclass:: longtable 316 317.. flat-table:: struct v4l2_ext_controls 318 :header-rows: 0 319 :stub-columns: 0 320 :widths: 1 1 2 321 322 * - union { 323 - (anonymous) 324 * - __u32 325 - ``which`` 326 - Which value of the control to get/set/try. 327 * - :cspan:`2` ``V4L2_CTRL_WHICH_CUR_VAL`` will return the current value of 328 the control, ``V4L2_CTRL_WHICH_DEF_VAL`` will return the default 329 value of the control and ``V4L2_CTRL_WHICH_REQUEST_VAL`` indicates that 330 these controls have to be retrieved from a request or tried/set for 331 a request. In the latter case the ``request_fd`` field contains the 332 file descriptor of the request that should be used. If the device 333 does not support requests, then ``EACCES`` will be returned. 334 335 When using ``V4L2_CTRL_WHICH_DEF_VAL`` be aware that you can only 336 get the default value of the control, you cannot set or try it. 337 338 For backwards compatibility you can also use a control class here 339 (see :ref:`ctrl-class`). In that case all controls have to 340 belong to that control class. This usage is deprecated, instead 341 just use ``V4L2_CTRL_WHICH_CUR_VAL``. There are some very old 342 drivers that do not yet support ``V4L2_CTRL_WHICH_CUR_VAL`` and 343 that require a control class here. You can test for such drivers 344 by setting ``which`` to ``V4L2_CTRL_WHICH_CUR_VAL`` and calling 345 :ref:`VIDIOC_TRY_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>` with a count of 0. 346 If that fails, then the driver does not support ``V4L2_CTRL_WHICH_CUR_VAL``. 347 * - __u32 348 - ``ctrl_class`` 349 - Deprecated name kept for backwards compatibility. Use ``which`` instead. 350 * - } 351 - 352 * - __u32 353 - ``count`` 354 - The number of controls in the controls array. May also be zero. 355 * - __u32 356 - ``error_idx`` 357 - Index of the failing control. Set by the driver in case of an error. 358 * - :cspan:`2` If the error is associated 359 with a particular control, then ``error_idx`` is set to the index 360 of that control. If the error is not related to a specific 361 control, or the validation step failed (see below), then 362 ``error_idx`` is set to ``count``. The value is undefined if the 363 ioctl returned 0 (success). 364 365 Before controls are read from/written to hardware a validation 366 step takes place: this checks if all controls in the list are 367 valid controls, if no attempt is made to write to a read-only 368 control or read from a write-only control, and any other up-front 369 checks that can be done without accessing the hardware. The exact 370 validations done during this step are driver dependent since some 371 checks might require hardware access for some devices, thus making 372 it impossible to do those checks up-front. However, drivers should 373 make a best-effort to do as many up-front checks as possible. 374 375 This check is done to avoid leaving the hardware in an 376 inconsistent state due to easy-to-avoid problems. But it leads to 377 another problem: the application needs to know whether an error 378 came from the validation step (meaning that the hardware was not 379 touched) or from an error during the actual reading from/writing 380 to hardware. 381 382 The, in hindsight quite poor, solution for that is to set 383 ``error_idx`` to ``count`` if the validation failed. This has the 384 unfortunate side-effect that it is not possible to see which 385 control failed the validation. If the validation was successful 386 and the error happened while accessing the hardware, then 387 ``error_idx`` is less than ``count`` and only the controls up to 388 ``error_idx-1`` were read or written correctly, and the state of 389 the remaining controls is undefined. 390 391 Since :ref:`VIDIOC_TRY_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>` does not access hardware there is 392 also no need to handle the validation step in this special way, so 393 ``error_idx`` will just be set to the control that failed the 394 validation step instead of to ``count``. This means that if 395 :ref:`VIDIOC_S_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>` fails with ``error_idx`` set to ``count``, 396 then you can call :ref:`VIDIOC_TRY_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>` to try to discover the 397 actual control that failed the validation step. Unfortunately, 398 there is no ``TRY`` equivalent for :ref:`VIDIOC_G_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>`. 399 * - __s32 400 - ``request_fd`` 401 - File descriptor of the request to be used by this operation. Only 402 valid if ``which`` is set to ``V4L2_CTRL_WHICH_REQUEST_VAL``. 403 If the device does not support requests, then ``EACCES`` will be returned. 404 If requests are supported but an invalid request file descriptor is 405 given, then ``EINVAL`` will be returned. 406 * - __u32 407 - ``reserved``\ [1] 408 - Reserved for future extensions. 409 410 Drivers and applications must set the array to zero. 411 * - struct :c:type:`v4l2_ext_control` * 412 - ``controls`` 413 - Pointer to an array of ``count`` v4l2_ext_control structures. 414 415 Ignored if ``count`` equals zero. 416 417.. tabularcolumns:: |p{7.3cm}|p{2.0cm}|p{8.0cm}| 418 419.. cssclass:: longtable 420 421.. _ctrl-class: 422 423.. flat-table:: Control classes 424 :header-rows: 0 425 :stub-columns: 0 426 :widths: 3 1 4 427 428 * - ``V4L2_CTRL_CLASS_USER`` 429 - 0x980000 430 - The class containing user controls. These controls are described 431 in :ref:`control`. All controls that can be set using the 432 :ref:`VIDIOC_S_CTRL <VIDIOC_G_CTRL>` and 433 :ref:`VIDIOC_G_CTRL <VIDIOC_G_CTRL>` ioctl belong to this 434 class. 435 * - ``V4L2_CTRL_CLASS_CODEC`` 436 - 0x990000 437 - The class containing stateful codec controls. These controls are 438 described in :ref:`codec-controls`. 439 * - ``V4L2_CTRL_CLASS_CAMERA`` 440 - 0x9a0000 441 - The class containing camera controls. These controls are described 442 in :ref:`camera-controls`. 443 * - ``V4L2_CTRL_CLASS_FM_TX`` 444 - 0x9b0000 445 - The class containing FM Transmitter (FM TX) controls. These 446 controls are described in :ref:`fm-tx-controls`. 447 * - ``V4L2_CTRL_CLASS_FLASH`` 448 - 0x9c0000 449 - The class containing flash device controls. These controls are 450 described in :ref:`flash-controls`. 451 * - ``V4L2_CTRL_CLASS_JPEG`` 452 - 0x9d0000 453 - The class containing JPEG compression controls. These controls are 454 described in :ref:`jpeg-controls`. 455 * - ``V4L2_CTRL_CLASS_IMAGE_SOURCE`` 456 - 0x9e0000 457 - The class containing image source controls. These controls are 458 described in :ref:`image-source-controls`. 459 * - ``V4L2_CTRL_CLASS_IMAGE_PROC`` 460 - 0x9f0000 461 - The class containing image processing controls. These controls are 462 described in :ref:`image-process-controls`. 463 * - ``V4L2_CTRL_CLASS_FM_RX`` 464 - 0xa10000 465 - The class containing FM Receiver (FM RX) controls. These controls 466 are described in :ref:`fm-rx-controls`. 467 * - ``V4L2_CTRL_CLASS_RF_TUNER`` 468 - 0xa20000 469 - The class containing RF tuner controls. These controls are 470 described in :ref:`rf-tuner-controls`. 471 * - ``V4L2_CTRL_CLASS_DETECT`` 472 - 0xa30000 473 - The class containing motion or object detection controls. These controls 474 are described in :ref:`detect-controls`. 475 * - ``V4L2_CTRL_CLASS_CODEC_STATELESS`` 476 - 0xa40000 477 - The class containing stateless codec controls. These controls are 478 described in :ref:`codec-stateless-controls`. 479 * - ``V4L2_CTRL_CLASS_COLORIMETRY`` 480 - 0xa50000 481 - The class containing colorimetry controls. These controls are 482 described in :ref:`colorimetry-controls`. 483 484Return Value 485============ 486 487On success 0 is returned, on error -1 and the ``errno`` variable is set 488appropriately. The generic error codes are described at the 489:ref:`Generic Error Codes <gen-errors>` chapter. 490 491EINVAL 492 The struct :c:type:`v4l2_ext_control` ``id`` is 493 invalid, or the struct :c:type:`v4l2_ext_controls` 494 ``which`` is invalid, or the struct 495 :c:type:`v4l2_ext_control` ``value`` was 496 inappropriate (e.g. the given menu index is not supported by the 497 driver), or the ``which`` field was set to ``V4L2_CTRL_WHICH_REQUEST_VAL`` 498 but the given ``request_fd`` was invalid or ``V4L2_CTRL_WHICH_REQUEST_VAL`` 499 is not supported by the kernel. 500 This error code is also returned by the 501 :ref:`VIDIOC_S_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>` and :ref:`VIDIOC_TRY_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>` ioctls if two or 502 more control values are in conflict. 503 504ERANGE 505 The struct :c:type:`v4l2_ext_control` ``value`` 506 is out of bounds. 507 508EBUSY 509 The control is temporarily not changeable, possibly because another 510 applications took over control of the device function this control 511 belongs to, or (if the ``which`` field was set to 512 ``V4L2_CTRL_WHICH_REQUEST_VAL``) the request was queued but not yet 513 completed. 514 515ENOSPC 516 The space reserved for the control's payload is insufficient. The 517 field ``size`` is set to a value that is enough to store the payload 518 and this error code is returned. 519 520EACCES 521 Attempt to try or set a read-only control, or to get a write-only 522 control, or to get a control from a request that has not yet been 523 completed. 524 525 Or the ``which`` field was set to ``V4L2_CTRL_WHICH_REQUEST_VAL`` but the 526 device does not support requests. 527 528 Or if there is an attempt to set an inactive control and the driver is 529 not capable of caching the new value until the control is active again. 530