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_rect` * 203 - ``p_rect`` 204 - A pointer to a struct :c:type:`v4l2_rect`. Valid if this control is 205 of type ``V4L2_CTRL_TYPE_RECT``. 206 * - struct :c:type:`v4l2_ctrl_h264_sps` * 207 - ``p_h264_sps`` 208 - A pointer to a struct :c:type:`v4l2_ctrl_h264_sps`. Valid if this control is 209 of type ``V4L2_CTRL_TYPE_H264_SPS``. 210 * - struct :c:type:`v4l2_ctrl_h264_pps` * 211 - ``p_h264_pps`` 212 - A pointer to a struct :c:type:`v4l2_ctrl_h264_pps`. Valid if this control is 213 of type ``V4L2_CTRL_TYPE_H264_PPS``. 214 * - struct :c:type:`v4l2_ctrl_h264_scaling_matrix` * 215 - ``p_h264_scaling_matrix`` 216 - A pointer to a struct :c:type:`v4l2_ctrl_h264_scaling_matrix`. Valid if this control is 217 of type ``V4L2_CTRL_TYPE_H264_SCALING_MATRIX``. 218 * - struct :c:type:`v4l2_ctrl_h264_pred_weights` * 219 - ``p_h264_pred_weights`` 220 - A pointer to a struct :c:type:`v4l2_ctrl_h264_pred_weights`. Valid if this control is 221 of type ``V4L2_CTRL_TYPE_H264_PRED_WEIGHTS``. 222 * - struct :c:type:`v4l2_ctrl_h264_slice_params` * 223 - ``p_h264_slice_params`` 224 - A pointer to a struct :c:type:`v4l2_ctrl_h264_slice_params`. Valid if this control is 225 of type ``V4L2_CTRL_TYPE_H264_SLICE_PARAMS``. 226 * - struct :c:type:`v4l2_ctrl_h264_decode_params` * 227 - ``p_h264_decode_params`` 228 - A pointer to a struct :c:type:`v4l2_ctrl_h264_decode_params`. Valid if this control is 229 of type ``V4L2_CTRL_TYPE_H264_DECODE_PARAMS``. 230 * - struct :c:type:`v4l2_ctrl_fwht_params` * 231 - ``p_fwht_params`` 232 - A pointer to a struct :c:type:`v4l2_ctrl_fwht_params`. Valid if this control is 233 of type ``V4L2_CTRL_TYPE_FWHT_PARAMS``. 234 * - struct :c:type:`v4l2_ctrl_vp8_frame` * 235 - ``p_vp8_frame`` 236 - A pointer to a struct :c:type:`v4l2_ctrl_vp8_frame`. Valid if this control is 237 of type ``V4L2_CTRL_TYPE_VP8_FRAME``. 238 * - struct :c:type:`v4l2_ctrl_mpeg2_sequence` * 239 - ``p_mpeg2_sequence`` 240 - A pointer to a struct :c:type:`v4l2_ctrl_mpeg2_sequence`. Valid if this control is 241 of type ``V4L2_CTRL_TYPE_MPEG2_SEQUENCE``. 242 * - struct :c:type:`v4l2_ctrl_mpeg2_picture` * 243 - ``p_mpeg2_picture`` 244 - A pointer to a struct :c:type:`v4l2_ctrl_mpeg2_picture`. Valid if this control is 245 of type ``V4L2_CTRL_TYPE_MPEG2_PICTURE``. 246 * - struct :c:type:`v4l2_ctrl_mpeg2_quantisation` * 247 - ``p_mpeg2_quantisation`` 248 - A pointer to a struct :c:type:`v4l2_ctrl_mpeg2_quantisation`. Valid if this control is 249 of type ``V4L2_CTRL_TYPE_MPEG2_QUANTISATION``. 250 * - struct :c:type:`v4l2_ctrl_vp9_compressed_hdr` * 251 - ``p_vp9_compressed_hdr_probs`` 252 - A pointer to a struct :c:type:`v4l2_ctrl_vp9_compressed_hdr`. Valid if this 253 control is of type ``V4L2_CTRL_TYPE_VP9_COMPRESSED_HDR``. 254 * - struct :c:type:`v4l2_ctrl_vp9_frame` * 255 - ``p_vp9_frame`` 256 - A pointer to a struct :c:type:`v4l2_ctrl_vp9_frame`. Valid if this 257 control is of type ``V4L2_CTRL_TYPE_VP9_FRAME``. 258 * - struct :c:type:`v4l2_ctrl_hdr10_cll_info` * 259 - ``p_hdr10_cll`` 260 - A pointer to a struct :c:type:`v4l2_ctrl_hdr10_cll_info`. Valid if this control is 261 of type ``V4L2_CTRL_TYPE_HDR10_CLL_INFO``. 262 * - struct :c:type:`v4l2_ctrl_hdr10_mastering_display` * 263 - ``p_hdr10_mastering`` 264 - A pointer to a struct :c:type:`v4l2_ctrl_hdr10_mastering_display`. Valid if this control is 265 of type ``V4L2_CTRL_TYPE_HDR10_MASTERING_DISPLAY``. 266 * - struct :c:type:`v4l2_ctrl_hevc_sps` * 267 - ``p_hevc_sps`` 268 - A pointer to a struct :c:type:`v4l2_ctrl_hevc_sps`. Valid if this 269 control is of type ``V4L2_CTRL_TYPE_HEVC_SPS``. 270 * - struct :c:type:`v4l2_ctrl_hevc_pps` * 271 - ``p_hevc_pps`` 272 - A pointer to a struct :c:type:`v4l2_ctrl_hevc_pps`. Valid if this 273 control is of type ``V4L2_CTRL_TYPE_HEVC_PPS``. 274 * - struct :c:type:`v4l2_ctrl_hevc_slice_params` * 275 - ``p_hevc_slice_params`` 276 - A pointer to a struct :c:type:`v4l2_ctrl_hevc_slice_params`. Valid if this 277 control is of type ``V4L2_CTRL_TYPE_HEVC_SLICE_PARAMS``. 278 * - struct :c:type:`v4l2_ctrl_hevc_scaling_matrix` * 279 - ``p_hevc_scaling_matrix`` 280 - A pointer to a struct :c:type:`v4l2_ctrl_hevc_scaling_matrix`. Valid if this 281 control is of type ``V4L2_CTRL_TYPE_HEVC_SCALING_MATRIX``. 282 * - struct :c:type:`v4l2_ctrl_hevc_decode_params` * 283 - ``p_hevc_decode_params`` 284 - A pointer to a struct :c:type:`v4l2_ctrl_hevc_decode_params`. Valid if this 285 control is of type ``V4L2_CTRL_TYPE_HEVC_DECODE_PARAMS``. 286 * - struct :c:type:`v4l2_ctrl_av1_sequence` * 287 - ``p_av1_sequence`` 288 - A pointer to a struct :c:type:`v4l2_ctrl_av1_sequence`. Valid if this control is 289 of type ``V4L2_CTRL_TYPE_AV1_SEQUENCE``. 290 * - struct :c:type:`v4l2_ctrl_av1_tile_group_entry` * 291 - ``p_av1_tile_group_entry`` 292 - A pointer to a struct :c:type:`v4l2_ctrl_av1_tile_group_entry`. Valid if this control is 293 of type ``V4L2_CTRL_TYPE_AV1_TILE_GROUP_ENTRY``. 294 * - struct :c:type:`v4l2_ctrl_av1_frame` * 295 - ``p_av1_frame`` 296 - A pointer to a struct :c:type:`v4l2_ctrl_av1_frame`. Valid if this control is 297 of type ``V4L2_CTRL_TYPE_AV1_FRAME``. 298 * - struct :c:type:`v4l2_ctrl_av1_film_grain` * 299 - ``p_av1_film_grain`` 300 - A pointer to a struct :c:type:`v4l2_ctrl_av1_film_grain`. Valid if this control is 301 of type ``V4L2_CTRL_TYPE_AV1_FILM_GRAIN``. 302 * - struct :c:type:`v4l2_ctrl_hdr10_cll_info` * 303 - ``p_hdr10_cll_info`` 304 - A pointer to a struct :c:type:`v4l2_ctrl_hdr10_cll_info`. Valid if this control is 305 of type ``V4L2_CTRL_TYPE_HDR10_CLL_INFO``. 306 * - struct :c:type:`v4l2_ctrl_hdr10_mastering_display` * 307 - ``p_hdr10_mastering_display`` 308 - A pointer to a struct :c:type:`v4l2_ctrl_hdr10_mastering_display`. Valid if this control is 309 of type ``V4L2_CTRL_TYPE_HDR10_MASTERING_DISPLAY``. 310 * - void * 311 - ``ptr`` 312 - A pointer to a compound type which can be an N-dimensional array 313 and/or a compound type (the control's type is >= 314 ``V4L2_CTRL_COMPOUND_TYPES``). Valid if 315 ``V4L2_CTRL_FLAG_HAS_PAYLOAD`` is set for this control. 316 * - } 317 - 318 319.. raw:: latex 320 321 \normalsize 322 323.. tabularcolumns:: |p{4.0cm}|p{2.5cm}|p{10.8cm}| 324 325.. c:type:: v4l2_ext_controls 326 327.. cssclass:: longtable 328 329.. flat-table:: struct v4l2_ext_controls 330 :header-rows: 0 331 :stub-columns: 0 332 :widths: 1 1 2 333 334 * - union { 335 - (anonymous) 336 * - __u32 337 - ``which`` 338 - Which value of the control to get/set/try. 339 * - :cspan:`2` ``V4L2_CTRL_WHICH_CUR_VAL`` will return the current value of 340 the control, ``V4L2_CTRL_WHICH_DEF_VAL`` will return the default 341 value of the control, ``V4L2_CTRL_WHICH_MIN_VAL`` will return the minimum 342 value of the control, and ``V4L2_CTRL_WHICH_MAX_VAL`` will return the maximum 343 value of the control. ``V4L2_CTRL_WHICH_REQUEST_VAL`` indicates that 344 the control value has to be retrieved from a request or tried/set for 345 a request. In that case the ``request_fd`` field contains the 346 file descriptor of the request that should be used. If the device 347 does not support requests, then ``EACCES`` will be returned. 348 349 When using ``V4L2_CTRL_WHICH_DEF_VAL``, ``V4L2_CTRL_WHICH_MIN_VAL`` 350 or ``V4L2_CTRL_WHICH_MAX_VAL`` be aware that you can only get the 351 default/minimum/maximum value of the control, you cannot set or try it. 352 353 Whether a control supports querying the minimum and maximum values using 354 ``V4L2_CTRL_WHICH_MIN_VAL`` and ``V4L2_CTRL_WHICH_MAX_VAL`` is indicated 355 by the ``V4L2_CTRL_FLAG_HAS_WHICH_MIN_MAX`` flag. Most non-compound 356 control types support this. For controls with compound types, the 357 definition of minimum/maximum values are provided by 358 the control documentation. If a compound control does not document the 359 meaning of minimum/maximum value, then querying the minimum or maximum 360 value will result in the error code -EINVAL. 361 362 For backwards compatibility you can also use a control class here 363 (see :ref:`ctrl-class`). In that case all controls have to 364 belong to that control class. This usage is deprecated, instead 365 just use ``V4L2_CTRL_WHICH_CUR_VAL``. There are some very old 366 drivers that do not yet support ``V4L2_CTRL_WHICH_CUR_VAL`` and 367 that require a control class here. You can test for such drivers 368 by setting ``which`` to ``V4L2_CTRL_WHICH_CUR_VAL`` and calling 369 :ref:`VIDIOC_TRY_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>` with a count of 0. 370 If that fails, then the driver does not support ``V4L2_CTRL_WHICH_CUR_VAL``. 371 * - __u32 372 - ``ctrl_class`` 373 - Deprecated name kept for backwards compatibility. Use ``which`` instead. 374 * - } 375 - 376 * - __u32 377 - ``count`` 378 - The number of controls in the controls array. May also be zero. 379 * - __u32 380 - ``error_idx`` 381 - Index of the failing control. Set by the driver in case of an error. 382 * - :cspan:`2` If the error is associated 383 with a particular control, then ``error_idx`` is set to the index 384 of that control. If the error is not related to a specific 385 control, or the validation step failed (see below), then 386 ``error_idx`` is set to ``count``. The value is undefined if the 387 ioctl returned 0 (success). 388 389 Before controls are read from/written to hardware a validation 390 step takes place: this checks if all controls in the list are 391 valid controls, if no attempt is made to write to a read-only 392 control or read from a write-only control, and any other up-front 393 checks that can be done without accessing the hardware. The exact 394 validations done during this step are driver dependent since some 395 checks might require hardware access for some devices, thus making 396 it impossible to do those checks up-front. However, drivers should 397 make a best-effort to do as many up-front checks as possible. 398 399 This check is done to avoid leaving the hardware in an 400 inconsistent state due to easy-to-avoid problems. But it leads to 401 another problem: the application needs to know whether an error 402 came from the validation step (meaning that the hardware was not 403 touched) or from an error during the actual reading from/writing 404 to hardware. 405 406 The, in hindsight quite poor, solution for that is to set 407 ``error_idx`` to ``count`` if the validation failed. This has the 408 unfortunate side-effect that it is not possible to see which 409 control failed the validation. If the validation was successful 410 and the error happened while accessing the hardware, then 411 ``error_idx`` is less than ``count`` and only the controls up to 412 ``error_idx-1`` were read or written correctly, and the state of 413 the remaining controls is undefined. 414 415 Since :ref:`VIDIOC_TRY_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>` does not access hardware there is 416 also no need to handle the validation step in this special way, so 417 ``error_idx`` will just be set to the control that failed the 418 validation step instead of to ``count``. This means that if 419 :ref:`VIDIOC_S_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>` fails with ``error_idx`` set to ``count``, 420 then you can call :ref:`VIDIOC_TRY_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>` to try to discover the 421 actual control that failed the validation step. Unfortunately, 422 there is no ``TRY`` equivalent for :ref:`VIDIOC_G_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>`. 423 * - __s32 424 - ``request_fd`` 425 - File descriptor of the request to be used by this operation. Only 426 valid if ``which`` is set to ``V4L2_CTRL_WHICH_REQUEST_VAL``. 427 If the device does not support requests, then ``EACCES`` will be returned. 428 If requests are supported but an invalid request file descriptor is 429 given, then ``EINVAL`` will be returned. 430 * - __u32 431 - ``reserved``\ [1] 432 - Reserved for future extensions. 433 434 Drivers and applications must set the array to zero. 435 * - struct :c:type:`v4l2_ext_control` * 436 - ``controls`` 437 - Pointer to an array of ``count`` v4l2_ext_control structures. 438 439 Ignored if ``count`` equals zero. 440 441.. tabularcolumns:: |p{7.3cm}|p{2.0cm}|p{8.0cm}| 442 443.. cssclass:: longtable 444 445.. _ctrl-class: 446 447.. flat-table:: Control classes 448 :header-rows: 0 449 :stub-columns: 0 450 :widths: 3 1 4 451 452 * - ``V4L2_CTRL_CLASS_USER`` 453 - 0x980000 454 - The class containing user controls. These controls are described 455 in :ref:`control`. All controls that can be set using the 456 :ref:`VIDIOC_S_CTRL <VIDIOC_G_CTRL>` and 457 :ref:`VIDIOC_G_CTRL <VIDIOC_G_CTRL>` ioctl belong to this 458 class. 459 * - ``V4L2_CTRL_CLASS_CODEC`` 460 - 0x990000 461 - The class containing stateful codec controls. These controls are 462 described in :ref:`codec-controls`. 463 * - ``V4L2_CTRL_CLASS_CAMERA`` 464 - 0x9a0000 465 - The class containing camera controls. These controls are described 466 in :ref:`camera-controls`. 467 * - ``V4L2_CTRL_CLASS_FM_TX`` 468 - 0x9b0000 469 - The class containing FM Transmitter (FM TX) controls. These 470 controls are described in :ref:`fm-tx-controls`. 471 * - ``V4L2_CTRL_CLASS_FLASH`` 472 - 0x9c0000 473 - The class containing flash device controls. These controls are 474 described in :ref:`flash-controls`. 475 * - ``V4L2_CTRL_CLASS_JPEG`` 476 - 0x9d0000 477 - The class containing JPEG compression controls. These controls are 478 described in :ref:`jpeg-controls`. 479 * - ``V4L2_CTRL_CLASS_IMAGE_SOURCE`` 480 - 0x9e0000 481 - The class containing image source controls. These controls are 482 described in :ref:`image-source-controls`. 483 * - ``V4L2_CTRL_CLASS_IMAGE_PROC`` 484 - 0x9f0000 485 - The class containing image processing controls. These controls are 486 described in :ref:`image-process-controls`. 487 * - ``V4L2_CTRL_CLASS_FM_RX`` 488 - 0xa10000 489 - The class containing FM Receiver (FM RX) controls. These controls 490 are described in :ref:`fm-rx-controls`. 491 * - ``V4L2_CTRL_CLASS_RF_TUNER`` 492 - 0xa20000 493 - The class containing RF tuner controls. These controls are 494 described in :ref:`rf-tuner-controls`. 495 * - ``V4L2_CTRL_CLASS_DETECT`` 496 - 0xa30000 497 - The class containing motion or object detection controls. These controls 498 are described in :ref:`detect-controls`. 499 * - ``V4L2_CTRL_CLASS_CODEC_STATELESS`` 500 - 0xa40000 501 - The class containing stateless codec controls. These controls are 502 described in :ref:`codec-stateless-controls`. 503 * - ``V4L2_CTRL_CLASS_COLORIMETRY`` 504 - 0xa50000 505 - The class containing colorimetry controls. These controls are 506 described in :ref:`colorimetry-controls`. 507 508Return Value 509============ 510 511On success 0 is returned, on error -1 and the ``errno`` variable is set 512appropriately. The generic error codes are described at the 513:ref:`Generic Error Codes <gen-errors>` chapter. 514 515EINVAL 516 The struct :c:type:`v4l2_ext_control` ``id`` is 517 invalid, or the struct :c:type:`v4l2_ext_controls` 518 ``which`` is invalid, or the struct 519 :c:type:`v4l2_ext_control` ``value`` was 520 inappropriate (e.g. the given menu index is not supported by the 521 driver), or the ``which`` field was set to ``V4L2_CTRL_WHICH_REQUEST_VAL`` 522 but the given ``request_fd`` was invalid or ``V4L2_CTRL_WHICH_REQUEST_VAL`` 523 is not supported by the kernel. 524 This error code is also returned by the 525 :ref:`VIDIOC_S_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>` and :ref:`VIDIOC_TRY_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>` ioctls if two or 526 more control values are in conflict. 527 528ERANGE 529 The struct :c:type:`v4l2_ext_control` ``value`` 530 is out of bounds. 531 532EBUSY 533 The control is temporarily not changeable, possibly because another 534 applications took over control of the device function this control 535 belongs to, or (if the ``which`` field was set to 536 ``V4L2_CTRL_WHICH_REQUEST_VAL``) the request was queued but not yet 537 completed. 538 539ENOSPC 540 The space reserved for the control's payload is insufficient. The 541 field ``size`` is set to a value that is enough to store the payload 542 and this error code is returned. 543 544EACCES 545 Attempt to try or set a read-only control, or to get a write-only 546 control, or to get a control from a request that has not yet been 547 completed. 548 549 Or the ``which`` field was set to ``V4L2_CTRL_WHICH_REQUEST_VAL`` but the 550 device does not support requests. 551 552 Or if there is an attempt to set an inactive control and the driver is 553 not capable of caching the new value until the control is active again. 554