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diff --git a/Documentation/media/uapi/v4l/vidioc-dbg-g-chip-info.rst b/Documentation/media/uapi/v4l/vidioc-dbg-g-chip-info.rst new file mode 100644 index 000000000000..f7e1b80af29e --- /dev/null +++ b/Documentation/media/uapi/v4l/vidioc-dbg-g-chip-info.rst @@ -0,0 +1,204 @@ +.. -*- coding: utf-8; mode: rst -*- + +.. _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 +======== + +.. cpp:function:: int ioctl( int fd, int request, struct v4l2_dbg_chip_info *argp ) + + +Arguments +========= + +``fd`` + File descriptor returned by :ref:`open() <func-open>`. + +``request`` + VIDIOC_DBG_G_CHIP_INFO + +``argp`` + + +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 +:ref:`v4l2_dbg_chip_info <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. + + +.. _name-v4l2-dbg-match: + +.. flat-table:: struct v4l2_dbg_match + :header-rows: 0 + :stub-columns: 0 + :widths: 1 1 1 2 + + + - .. row 1 + + - __u32 + + - ``type`` + + - See :ref:`name-chip-match-types` for a list of possible types. + + - .. row 2 + + - union + + - (anonymous) + + - .. row 3 + + - + - __u32 + + - ``addr`` + + - Match a chip by this number, interpreted according to the ``type`` + field. + + - .. row 4 + + - + - char + + - ``name[32]`` + + - Match a chip by this name, interpreted according to the ``type`` + field. Currently unused. + + + +.. _v4l2-dbg-chip-info: + +.. flat-table:: struct v4l2_dbg_chip_info + :header-rows: 0 + :stub-columns: 0 + :widths: 1 1 2 + + + - .. row 1 + + - struct v4l2_dbg_match + + - ``match`` + + - How to match the chip, see :ref:`name-v4l2-dbg-match`. + + - .. row 2 + + - char + + - ``name[32]`` + + - The name of the chip. + + - .. row 3 + + - __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. + + - .. row 4 + + - __u32 + + - ``reserved[8]`` + + - Reserved fields, both application and driver must set these to 0. + + + +.. _name-chip-match-types: + +.. flat-table:: Chip Match Types + :header-rows: 0 + :stub-columns: 0 + :widths: 3 1 4 + + + - .. row 1 + + - ``V4L2_CHIP_MATCH_BRIDGE`` + + - 0 + + - Match the nth chip on the card, zero for the bridge chip. Does not + match sub-devices. + + - .. row 2 + + - ``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. |