Documentation/linux_tv/media/v4l/vidioc-enum-framesizes.rst

   1 .. -*- coding: utf-8; mode: rst -*-
   2
   3 .. _VIDIOC_ENUM_FRAMESIZES:
   4
   5 ****************************
   6 ioctl VIDIOC_ENUM_FRAMESIZES
   7 ****************************
   8
   9 *man VIDIOC_ENUM_FRAMESIZES(2)*
  10
  11 Enumerate frame sizes
  12
  13
  14 Synopsis
  15 ========
  16
  17 .. cpp:function:: int ioctl( int fd, int request, struct v4l2_frmsizeenum *argp )
  18
  19 Arguments
  20 =========
  21
  22 ``fd``
  23     File descriptor returned by :ref:`open() <func-open>`.
  24
  25 ``request``
  26     VIDIOC_ENUM_FRAMESIZES
  27
  28 ``argp``
  29     Pointer to a struct :ref:`v4l2_frmsizeenum <v4l2-frmsizeenum>`
  30     that contains an index and pixel format and receives a frame width
  31     and height.
  32
  33
  34 Description
  35 ===========
  36
  37 This ioctl allows applications to enumerate all frame sizes (i. e. width
  38 and height in pixels) that the device supports for the given pixel
  39 format.
  40
  41 The supported pixel formats can be obtained by using the
  42 :ref:`VIDIOC_ENUM_FMT` function.
  43
  44 The return value and the content of the ``v4l2_frmsizeenum.type`` field
  45 depend on the type of frame sizes the device supports. Here are the
  46 semantics of the function for the different cases:
  47
  48 -  **Discrete:** The function returns success if the given index value
  49    (zero-based) is valid. The application should increase the index by
  50    one for each call until ``EINVAL`` is returned. The
  51    ``v4l2_frmsizeenum.type`` field is set to
  52    ``V4L2_FRMSIZE_TYPE_DISCRETE`` by the driver. Of the union only the
  53    ``discrete`` member is valid.
  54
  55 -  **Step-wise:** The function returns success if the given index value
  56    is zero and ``EINVAL`` for any other index value. The
  57    ``v4l2_frmsizeenum.type`` field is set to
  58    ``V4L2_FRMSIZE_TYPE_STEPWISE`` by the driver. Of the union only the
  59    ``stepwise`` member is valid.
  60
  61 -  **Continuous:** This is a special case of the step-wise type above.
  62    The function returns success if the given index value is zero and
  63    ``EINVAL`` for any other index value. The ``v4l2_frmsizeenum.type``
  64    field is set to ``V4L2_FRMSIZE_TYPE_CONTINUOUS`` by the driver. Of
  65    the union only the ``stepwise`` member is valid and the
  66    ``step_width`` and ``step_height`` values are set to 1.
  67
  68 When the application calls the function with index zero, it must check
  69 the ``type`` field to determine the type of frame size enumeration the
  70 device supports. Only for the ``V4L2_FRMSIZE_TYPE_DISCRETE`` type does
  71 it make sense to increase the index value to receive more frame sizes.
  72
  73 Note that the order in which the frame sizes are returned has no special
  74 meaning. In particular does it not say anything about potential default
  75 format sizes.
  76
  77 Applications can assume that the enumeration data does not change
  78 without any interaction from the application itself. This means that the
  79 enumeration data is consistent if the application does not perform any
  80 other ioctl calls while it runs the frame size enumeration.
  81
  82
  83 Structs
  84 =======
  85
  86 In the structs below, *IN* denotes a value that has to be filled in by
  87 the application, *OUT* denotes values that the driver fills in. The
  88 application should zero out all members except for the *IN* fields.
  89
  90
  91 .. _v4l2-frmsize-discrete:
  92
  93 .. flat-table:: struct v4l2_frmsize_discrete
  94     :header-rows:  0
  95     :stub-columns: 0
  96     :widths:       1 1 2
  97
  98
  99     -  .. row 1
 100
 101        -  __u32
 102
 103        -  ``width``
 104
 105        -  Width of the frame [pixel].
 106
 107     -  .. row 2
 108
 109        -  __u32
 110
 111        -  ``height``
 112
 113        -  Height of the frame [pixel].
 114
 115
 116
 117 .. _v4l2-frmsize-stepwise:
 118
 119 .. flat-table:: struct v4l2_frmsize_stepwise
 120     :header-rows:  0
 121     :stub-columns: 0
 122     :widths:       1 1 2
 123
 124
 125     -  .. row 1
 126
 127        -  __u32
 128
 129        -  ``min_width``
 130
 131        -  Minimum frame width [pixel].
 132
 133     -  .. row 2
 134
 135        -  __u32
 136
 137        -  ``max_width``
 138
 139        -  Maximum frame width [pixel].
 140
 141     -  .. row 3
 142
 143        -  __u32
 144
 145        -  ``step_width``
 146
 147        -  Frame width step size [pixel].
 148
 149     -  .. row 4
 150
 151        -  __u32
 152
 153        -  ``min_height``
 154
 155        -  Minimum frame height [pixel].
 156
 157     -  .. row 5
 158
 159        -  __u32
 160
 161        -  ``max_height``
 162
 163        -  Maximum frame height [pixel].
 164
 165     -  .. row 6
 166
 167        -  __u32
 168
 169        -  ``step_height``
 170
 171        -  Frame height step size [pixel].
 172
 173
 174
 175 .. _v4l2-frmsizeenum:
 176
 177 .. flat-table:: struct v4l2_frmsizeenum
 178     :header-rows:  0
 179     :stub-columns: 0
 180
 181
 182     -  .. row 1
 183
 184        -  __u32
 185
 186        -  ``index``
 187
 188        -
 189        -  IN: Index of the given frame size in the enumeration.
 190
 191     -  .. row 2
 192
 193        -  __u32
 194
 195        -  ``pixel_format``
 196
 197        -
 198        -  IN: Pixel format for which the frame sizes are enumerated.
 199
 200     -  .. row 3
 201
 202        -  __u32
 203
 204        -  ``type``
 205
 206        -
 207        -  OUT: Frame size type the device supports.
 208
 209     -  .. row 4
 210
 211        -  union
 212
 213        -
 214        -
 215        -  OUT: Frame size with the given index.
 216
 217     -  .. row 5
 218
 219        -
 220        -  struct :ref:`v4l2_frmsize_discrete <v4l2-frmsize-discrete>`
 221
 222        -  ``discrete``
 223
 224        -
 225
 226     -  .. row 6
 227
 228        -
 229        -  struct :ref:`v4l2_frmsize_stepwise <v4l2-frmsize-stepwise>`
 230
 231        -  ``stepwise``
 232
 233        -
 234
 235     -  .. row 7
 236
 237        -  __u32
 238
 239        -  ``reserved[2]``
 240
 241        -
 242        -  Reserved space for future use. Must be zeroed by drivers and
 243           applications.
 244
 245
 246
 247 Enums
 248 =====
 249
 250
 251 .. _v4l2-frmsizetypes:
 252
 253 .. flat-table:: enum v4l2_frmsizetypes
 254     :header-rows:  0
 255     :stub-columns: 0
 256     :widths:       3 1 4
 257
 258
 259     -  .. row 1
 260
 261        -  ``V4L2_FRMSIZE_TYPE_DISCRETE``
 262
 263        -  1
 264
 265        -  Discrete frame size.
 266
 267     -  .. row 2
 268
 269        -  ``V4L2_FRMSIZE_TYPE_CONTINUOUS``
 270
 271        -  2
 272
 273        -  Continuous frame size.
 274
 275     -  .. row 3
 276
 277        -  ``V4L2_FRMSIZE_TYPE_STEPWISE``
 278
 279        -  3
 280
 281        -  Step-wise defined frame size.
 282
 283
 284
 285 Return Value
 286 ============
 287
 288 On success 0 is returned, on error -1 and the ``errno`` variable is set
 289 appropriately. The generic error codes are described at the
 290 :ref:`Generic Error Codes <gen-errors>` chapter.
 291
 292
 293 .. ------------------------------------------------------------------------------
 294 .. This file was automatically converted from DocBook-XML with the dbxml
 295 .. library (https://github.com/return42/sphkerneldoc). The origin XML comes
 296 .. from the linux kernel, refer to:
 297 ..
 298 .. * https://github.com/torvalds/linux/tree/master/Documentation/DocBook
 299 .. ------------------------------------------------------------------------------