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| -rw-r--r-- | Documentation/userspace-api/media/v4l/vidioc-dbg-g-chip-info.rst | 155 |
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diff --git a/Documentation/userspace-api/media/v4l/vidioc-dbg-g-chip-info.rst b/Documentation/userspace-api/media/v4l/vidioc-dbg-g-chip-info.rst new file mode 100644 index 0000000000..1a1e093936 --- /dev/null +++ b/Documentation/userspace-api/media/v4l/vidioc-dbg-g-chip-info.rst @@ -0,0 +1,155 @@ +.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later +.. c:namespace:: V4L + +.. _VIDIOC_DBG_G_CHIP_INFO: + +**************************** +ioctl VIDIOC_DBG_G_CHIP_INFO +**************************** + +Name +==== + +VIDIOC_DBG_G_CHIP_INFO - Identify the chips on a TV card + +Synopsis +======== + +.. c:macro:: VIDIOC_DBG_G_CHIP_INFO + +``int ioctl(int fd, VIDIOC_DBG_G_CHIP_INFO, struct v4l2_dbg_chip_info *argp)`` + +Arguments +========= + +``fd`` + File descriptor returned by :c:func:`open()`. + +``argp`` + Pointer to struct :c:type:`v4l2_dbg_chip_info`. + +Description +=========== + +.. note:: + + This is an :ref:`experimental` interface and may + change in the future. + +For driver debugging purposes this ioctl allows test applications to +query the driver about the chips present on the TV card. Regular +applications must not use it. When you found a chip specific bug, please +contact the linux-media mailing list +(`https://linuxtv.org/lists.php <https://linuxtv.org/lists.php>`__) +so it can be fixed. + +Additionally the Linux kernel must be compiled with the +``CONFIG_VIDEO_ADV_DEBUG`` option to enable this ioctl. + +To query the driver applications must initialize the ``match.type`` and +``match.addr`` or ``match.name`` fields of a struct +:c:type:`v4l2_dbg_chip_info` and call +:ref:`VIDIOC_DBG_G_CHIP_INFO` with a pointer to this structure. On success +the driver stores information about the selected chip in the ``name`` +and ``flags`` fields. + +When ``match.type`` is ``V4L2_CHIP_MATCH_BRIDGE``, ``match.addr`` +selects the nth bridge 'chip' on the TV card. You can enumerate all +chips by starting at zero and incrementing ``match.addr`` by one until +:ref:`VIDIOC_DBG_G_CHIP_INFO` fails with an ``EINVAL`` error code. The number +zero always selects the bridge chip itself, e. g. the chip connected to +the PCI or USB bus. Non-zero numbers identify specific parts of the +bridge chip such as an AC97 register block. + +When ``match.type`` is ``V4L2_CHIP_MATCH_SUBDEV``, ``match.addr`` +selects the nth sub-device. This allows you to enumerate over all +sub-devices. + +On success, the ``name`` field will contain a chip name and the +``flags`` field will contain ``V4L2_CHIP_FL_READABLE`` if the driver +supports reading registers from the device or ``V4L2_CHIP_FL_WRITABLE`` +if the driver supports writing registers to the device. + +We recommended the v4l2-dbg utility over calling this ioctl directly. It +is available from the LinuxTV v4l-dvb repository; see +`https://linuxtv.org/repo/ <https://linuxtv.org/repo/>`__ for access +instructions. + +.. tabularcolumns:: |p{3.5cm}|p{3.5cm}|p{3.5cm}|p{6.6cm}| + +.. _name-v4l2-dbg-match: + +.. flat-table:: struct v4l2_dbg_match + :header-rows: 0 + :stub-columns: 0 + :widths: 1 1 2 + + * - __u32 + - ``type`` + - See :ref:`name-chip-match-types` for a list of possible types. + * - union { + - (anonymous) + * - __u32 + - ``addr`` + - Match a chip by this number, interpreted according to the ``type`` + field. + * - char + - ``name[32]`` + - Match a chip by this name, interpreted according to the ``type`` + field. Currently unused. + * - } + - + + +.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.5cm}| + +.. c:type:: v4l2_dbg_chip_info + +.. flat-table:: struct v4l2_dbg_chip_info + :header-rows: 0 + :stub-columns: 0 + :widths: 1 1 2 + + * - struct v4l2_dbg_match + - ``match`` + - How to match the chip, see :ref:`name-v4l2-dbg-match`. + * - char + - ``name[32]`` + - The name of the chip. + * - __u32 + - ``flags`` + - Set by the driver. If ``V4L2_CHIP_FL_READABLE`` is set, then the + driver supports reading registers from the device. If + ``V4L2_CHIP_FL_WRITABLE`` is set, then it supports writing + registers. + * - __u32 + - ``reserved[8]`` + - Reserved fields, both application and driver must set these to 0. + + +.. tabularcolumns:: |p{6.6cm}|p{2.2cm}|p{8.5cm}| + +.. _name-chip-match-types: + +.. flat-table:: Chip Match Types + :header-rows: 0 + :stub-columns: 0 + :widths: 3 1 4 + + * - ``V4L2_CHIP_MATCH_BRIDGE`` + - 0 + - Match the nth chip on the card, zero for the bridge chip. Does not + match sub-devices. + * - ``V4L2_CHIP_MATCH_SUBDEV`` + - 4 + - Match the nth sub-device. + +Return Value +============ + +On success 0 is returned, on error -1 and the ``errno`` variable is set +appropriately. The generic error codes are described at the +:ref:`Generic Error Codes <gen-errors>` chapter. + +EINVAL + The ``match_type`` is invalid or no device could be matched. |