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