161 lines
4.4 KiB
ReStructuredText
Executable file
161 lines
4.4 KiB
ReStructuredText
Executable file
.. -*- coding: utf-8; mode: rst -*-
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.. _VIDIOC_DBG_G_CHIP_INFO:
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****************************
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ioctl VIDIOC_DBG_G_CHIP_INFO
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****************************
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Name
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====
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VIDIOC_DBG_G_CHIP_INFO - Identify the chips on a TV card
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Synopsis
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========
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.. c:function:: int ioctl( int fd, VIDIOC_DBG_G_CHIP_INFO, struct v4l2_dbg_chip_info *argp )
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:name: VIDIOC_DBG_G_CHIP_INFO
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Arguments
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=========
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``fd``
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File descriptor returned by :ref:`open() <func-open>`.
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``argp``
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Pointer to struct :c:type:`v4l2_dbg_chip_info`.
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Description
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===========
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.. note::
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This is an :ref:`experimental` interface and may
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change in the future.
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For driver debugging purposes this ioctl allows test applications to
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query the driver about the chips present on the TV card. Regular
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applications must not use it. When you found a chip specific bug, please
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contact the linux-media mailing list
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(`https://linuxtv.org/lists.php <https://linuxtv.org/lists.php>`__)
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so it can be fixed.
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Additionally the Linux kernel must be compiled with the
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``CONFIG_VIDEO_ADV_DEBUG`` option to enable this ioctl.
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To query the driver applications must initialize the ``match.type`` and
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``match.addr`` or ``match.name`` fields of a struct
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:c:type:`v4l2_dbg_chip_info` and call
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:ref:`VIDIOC_DBG_G_CHIP_INFO` with a pointer to this structure. On success
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the driver stores information about the selected chip in the ``name``
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and ``flags`` fields.
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When ``match.type`` is ``V4L2_CHIP_MATCH_BRIDGE``, ``match.addr``
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selects the nth bridge 'chip' on the TV card. You can enumerate all
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chips by starting at zero and incrementing ``match.addr`` by one until
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:ref:`VIDIOC_DBG_G_CHIP_INFO` fails with an ``EINVAL`` error code. The number
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zero always selects the bridge chip itself, e. g. the chip connected to
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the PCI or USB bus. Non-zero numbers identify specific parts of the
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bridge chip such as an AC97 register block.
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When ``match.type`` is ``V4L2_CHIP_MATCH_SUBDEV``, ``match.addr``
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selects the nth sub-device. This allows you to enumerate over all
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sub-devices.
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On success, the ``name`` field will contain a chip name and the
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``flags`` field will contain ``V4L2_CHIP_FL_READABLE`` if the driver
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supports reading registers from the device or ``V4L2_CHIP_FL_WRITABLE``
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if the driver supports writing registers to the device.
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We recommended the v4l2-dbg utility over calling this ioctl directly. It
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is available from the LinuxTV v4l-dvb repository; see
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`https://linuxtv.org/repo/ <https://linuxtv.org/repo/>`__ for access
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instructions.
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.. tabularcolumns:: |p{3.5cm}|p{3.5cm}|p{3.5cm}|p{7.0cm}|
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.. _name-v4l2-dbg-match:
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.. flat-table:: struct v4l2_dbg_match
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:header-rows: 0
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:stub-columns: 0
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:widths: 1 1 1 2
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* - __u32
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- ``type``
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- See :ref:`name-chip-match-types` for a list of possible types.
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* - union
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- (anonymous)
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* -
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- __u32
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- ``addr``
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- Match a chip by this number, interpreted according to the ``type``
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field.
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* -
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- char
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- ``name[32]``
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- Match a chip by this name, interpreted according to the ``type``
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field. Currently unused.
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.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.7cm}|
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.. c:type:: v4l2_dbg_chip_info
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.. flat-table:: struct v4l2_dbg_chip_info
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:header-rows: 0
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:stub-columns: 0
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:widths: 1 1 2
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* - struct v4l2_dbg_match
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- ``match``
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- How to match the chip, see :ref:`name-v4l2-dbg-match`.
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* - char
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- ``name[32]``
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- The name of the chip.
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* - __u32
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- ``flags``
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- Set by the driver. If ``V4L2_CHIP_FL_READABLE`` is set, then the
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driver supports reading registers from the device. If
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``V4L2_CHIP_FL_WRITABLE`` is set, then it supports writing
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registers.
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* - __u32
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- ``reserved[8]``
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- Reserved fields, both application and driver must set these to 0.
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.. tabularcolumns:: |p{6.6cm}|p{2.2cm}|p{8.7cm}|
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.. _name-chip-match-types:
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.. flat-table:: Chip Match Types
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:header-rows: 0
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:stub-columns: 0
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:widths: 3 1 4
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* - ``V4L2_CHIP_MATCH_BRIDGE``
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- 0
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- Match the nth chip on the card, zero for the bridge chip. Does not
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match sub-devices.
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* - ``V4L2_CHIP_MATCH_SUBDEV``
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- 4
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- Match the nth sub-device.
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Return Value
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============
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On success 0 is returned, on error -1 and the ``errno`` variable is set
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appropriately. The generic error codes are described at the
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:ref:`Generic Error Codes <gen-errors>` chapter.
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EINVAL
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The ``match_type`` is invalid or no device could be matched.
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