Documentation/linux_tv/media/v4l/vidioc-dbg-g-chip-info.rst

   1 .. -*- coding: utf-8; mode: rst -*-
   2
   3 .. _VIDIOC_DBG_G_CHIP_INFO:
   4
   5 ****************************
   6 ioctl VIDIOC_DBG_G_CHIP_INFO
   7 ****************************
   8
   9 *man VIDIOC_DBG_G_CHIP_INFO(2)*
  10
  11 Identify the chips on a TV card
  12
  13
  14 Synopsis
  15 ========
  16
  17 .. cpp:function:: int ioctl( int fd, int request, struct v4l2_dbg_chip_info *argp )
  18
  19 Arguments
  20 =========
  21
  22 ``fd``
  23     File descriptor returned by :ref:`open() <func-open>`.
  24
  25 ``request``
  26     VIDIOC_DBG_G_CHIP_INFO
  27
  28 ``argp``
  29
  30
  31 Description
  32 ===========
  33
  34     **Note**
  35
  36     This is an :ref:`experimental` interface and may
  37     change in the future.
  38
  39 For driver debugging purposes this ioctl allows test applications to
  40 query the driver about the chips present on the TV card. Regular
  41 applications must not use it. When you found a chip specific bug, please
  42 contact the linux-media mailing list
  43 (`https://linuxtv.org/lists.php <https://linuxtv.org/lists.php>`__)
  44 so it can be fixed.
  45
  46 Additionally the Linux kernel must be compiled with the
  47 ``CONFIG_VIDEO_ADV_DEBUG`` option to enable this ioctl.
  48
  49 To query the driver applications must initialize the ``match.type`` and
  50 ``match.addr`` or ``match.name`` fields of a struct
  51 :ref:`v4l2_dbg_chip_info <v4l2-dbg-chip-info>` and call
  52 :ref:`VIDIOC_DBG_G_CHIP_INFO` with a pointer to this structure. On success
  53 the driver stores information about the selected chip in the ``name``
  54 and ``flags`` fields.
  55
  56 When ``match.type`` is ``V4L2_CHIP_MATCH_BRIDGE``, ``match.addr``
  57 selects the nth bridge 'chip' on the TV card. You can enumerate all
  58 chips by starting at zero and incrementing ``match.addr`` by one until
  59 :ref:`VIDIOC_DBG_G_CHIP_INFO` fails with an ``EINVAL`` error code. The number
  60 zero always selects the bridge chip itself, e. g. the chip connected to
  61 the PCI or USB bus. Non-zero numbers identify specific parts of the
  62 bridge chip such as an AC97 register block.
  63
  64 When ``match.type`` is ``V4L2_CHIP_MATCH_SUBDEV``, ``match.addr``
  65 selects the nth sub-device. This allows you to enumerate over all
  66 sub-devices.
  67
  68 On success, the ``name`` field will contain a chip name and the
  69 ``flags`` field will contain ``V4L2_CHIP_FL_READABLE`` if the driver
  70 supports reading registers from the device or ``V4L2_CHIP_FL_WRITABLE``
  71 if the driver supports writing registers to the device.
  72
  73 We recommended the v4l2-dbg utility over calling this ioctl directly. It
  74 is available from the LinuxTV v4l-dvb repository; see
  75 `https://linuxtv.org/repo/ <https://linuxtv.org/repo/>`__ for access
  76 instructions.
  77
  78
  79 .. _name-v4l2-dbg-match:
  80
  81 .. flat-table:: struct v4l2_dbg_match
  82     :header-rows:  0
  83     :stub-columns: 0
  84     :widths:       1 1 1 2
  85
  86
  87     -  .. row 1
  88
  89        -  __u32
  90
  91        -  ``type``
  92
  93        -  See :ref:`name-chip-match-types` for a list of possible types.
  94
  95     -  .. row 2
  96
  97        -  union
  98
  99        -  (anonymous)
 100
 101     -  .. row 3
 102
 103        -
 104        -  __u32
 105
 106        -  ``addr``
 107
 108        -  Match a chip by this number, interpreted according to the ``type``
 109           field.
 110
 111     -  .. row 4
 112
 113        -
 114        -  char
 115
 116        -  ``name[32]``
 117
 118        -  Match a chip by this name, interpreted according to the ``type``
 119           field. Currently unused.
 120
 121
 122
 123 .. _v4l2-dbg-chip-info:
 124
 125 .. flat-table:: struct v4l2_dbg_chip_info
 126     :header-rows:  0
 127     :stub-columns: 0
 128     :widths:       1 1 2
 129
 130
 131     -  .. row 1
 132
 133        -  struct v4l2_dbg_match
 134
 135        -  ``match``
 136
 137        -  How to match the chip, see :ref:`name-v4l2-dbg-match`.
 138
 139     -  .. row 2
 140
 141        -  char
 142
 143        -  ``name[32]``
 144
 145        -  The name of the chip.
 146
 147     -  .. row 3
 148
 149        -  __u32
 150
 151        -  ``flags``
 152
 153        -  Set by the driver. If ``V4L2_CHIP_FL_READABLE`` is set, then the
 154           driver supports reading registers from the device. If
 155           ``V4L2_CHIP_FL_WRITABLE`` is set, then it supports writing
 156           registers.
 157
 158     -  .. row 4
 159
 160        -  __u32
 161
 162        -  ``reserved[8]``
 163
 164        -  Reserved fields, both application and driver must set these to 0.
 165
 166
 167
 168 .. _name-chip-match-types:
 169
 170 .. flat-table:: Chip Match Types
 171     :header-rows:  0
 172     :stub-columns: 0
 173     :widths:       3 1 4
 174
 175
 176     -  .. row 1
 177
 178        -  ``V4L2_CHIP_MATCH_BRIDGE``
 179
 180        -  0
 181
 182        -  Match the nth chip on the card, zero for the bridge chip. Does not
 183           match sub-devices.
 184
 185     -  .. row 2
 186
 187        -  ``V4L2_CHIP_MATCH_SUBDEV``
 188
 189        -  4
 190
 191        -  Match the nth sub-device.
 192
 193
 194
 195 Return Value
 196 ============
 197
 198 On success 0 is returned, on error -1 and the ``errno`` variable is set
 199 appropriately. The generic error codes are described at the
 200 :ref:`Generic Error Codes <gen-errors>` chapter.
 201
 202 EINVAL
 203     The ``match_type`` is invalid or no device could be matched.