docs: driver-api: add iio hw consumer section

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HW consumer

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An IIO device can be directly connected to another device in hardware. in this

case the buffers between IIO provider and IIO consumer are handled by hardware.

The Industrial I/O HW consumer offers a way to bond these IIO devices without

software buffer for data. The implementation can be found under

:file:`drivers/iio/buffer/hw-consumer.c`

* struct :c:type:`iio_hw_consumer` — Hardware consumer structure

* :c:func:`iio_hw_consumer_alloc` — Allocate IIO hardware consumer

* :c:func:`iio_hw_consumer_free` — Free IIO hardware consumer

* :c:func:`iio_hw_consumer_enable` — Enable IIO hardware consumer

* :c:func:`iio_hw_consumer_disable` — Disable IIO hardware consumer

HW consumer setup

=================

As standard IIO device the implementation is based on IIO provider/consumer.

A typical IIO HW consumer setup looks like this::

	static struct iio_hw_consumer *hwc;

	static const struct iio_info adc_info = {

		.read_raw = adc_read_raw,

	};

	static int adc_read_raw(struct iio_dev *indio_dev,

				struct iio_chan_spec const *chan, int *val,

				int *val2, long mask)

	{

		ret = iio_hw_consumer_enable(hwc);

		/* Acquire data */

		ret = iio_hw_consumer_disable(hwc);

	}

	static int adc_probe(struct platform_device *pdev)

	{

		hwc = devm_iio_hw_consumer_alloc(&iio->dev);

	}

More details

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.. kernel-doc:: include/linux/iio/hw-consumer.h

.. kernel-doc:: drivers/iio/buffer/industrialio-hw-consumer.c

   :export:

   buffers

   triggers

   triggered-buffers

   hw-consumer