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Linux/Documentation/userspace-api/media/v4l/vidioc-queryctrl.rst

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Diff markup

Differences between /Documentation/userspace-api/media/v4l/vidioc-queryctrl.rst (Version linux-6.12-rc7) and /Documentation/userspace-api/media/v4l/vidioc-queryctrl.rst (Version linux-4.18.20)


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

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