iio_simple_dummy_buffer.c

  1// SPDX-License-Identifier: GPL-2.0-only
  2/*
  3 * Copyright (c) 2011 Jonathan Cameron
  4 *
  5 * Buffer handling elements of industrial I/O reference driver.
  6 * Uses the kfifo buffer.
  7 *
  8 * To test without hardware use the sysfs trigger.
  9 */
 10
 11#include <linux/kernel.h>
 12#include <linux/export.h>
 13#include <linux/slab.h>
 14#include <linux/interrupt.h>
 15#include <linux/irq.h>
 16#include <linux/bitmap.h>
 17
 18#include <linux/iio/iio.h>
 19#include <linux/iio/buffer.h>
 20#include <linux/iio/trigger_consumer.h>
 21#include <linux/iio/triggered_buffer.h>
 22
 23#include "iio_simple_dummy.h"
 24
 25/* Some fake data */
 26
 27static const s16 fakedata[] = {
 28	[DUMMY_INDEX_VOLTAGE_0] = 7,
 29	[DUMMY_INDEX_DIFFVOLTAGE_1M2] = -33,
 30	[DUMMY_INDEX_DIFFVOLTAGE_3M4] = -2,
 31	[DUMMY_INDEX_ACCELX] = 344,
 32};
 33
 34struct dummy_scan {
 35	s16 data[ARRAY_SIZE(fakedata)];
 36	aligned_s64 timestamp;
 37};
 38
 39/**
 40 * iio_simple_dummy_trigger_h() - the trigger handler function
 41 * @irq: the interrupt number
 42 * @p: private data - always a pointer to the poll func.
 43 *
 44 * This is the guts of buffered capture. On a trigger event occurring,
 45 * if the pollfunc is attached then this handler is called as a threaded
 46 * interrupt (and hence may sleep). It is responsible for grabbing data
 47 * from the device and pushing it into the associated buffer.
 48 */
 49static irqreturn_t iio_simple_dummy_trigger_h(int irq, void *p)
 50{
 51	struct iio_poll_func *pf = p;
 52	struct iio_dev *indio_dev = pf->indio_dev;
 53	struct dummy_scan *scan;
 54	int i = 0, j;
 55
 56	/*
 57	 * Note that some buses such as SPI require DMA safe buffers which
 58	 * cannot be on the stack. Two easy ways to do this:
 59	 *  - Local kzalloc (as done here)
 60	 *  - A buffer at the end of the structure accessed via iio_priv()
 61	 *    that is marked __aligned(IIO_DMA_MINALIGN).
 62	 */
 63	scan = kzalloc(sizeof(*scan), GFP_KERNEL);
 64	if (!scan)
 65		goto done;
 66
 67	/*
 68	 * Three common options here:
 69	 * hardware scans:
 70	 *   certain combinations of channels make up a fast read. The capture
 71	 *   will consist of all of them. Hence we just call the grab data
 72	 *   function and fill the buffer without processing.
 73	 * software scans:
 74	 *   can be considered to be random access so efficient reading is just
 75	 *   a case of minimal bus transactions.
 76	 * software culled hardware scans:
 77	 *   occasionally a driver may process the nearest hardware scan to avoid
 78	 *   storing elements that are not desired. This is the fiddliest option
 79	 *   by far.
 80	 * Here let's pretend we have random access. And the values are in the
 81	 * constant table fakedata.
 82	 */
 83	iio_for_each_active_channel(indio_dev, j)
 84		scan->data[i++] = fakedata[j];
 85
 86	iio_push_to_buffers_with_ts(indio_dev, scan, sizeof(*scan),
 87				    iio_get_time_ns(indio_dev));
 88
 89	kfree(scan);
 90done:
 91	/*
 92	 * Tell the core we are done with this trigger and ready for the
 93	 * next one.
 94	 */
 95	iio_trigger_notify_done(indio_dev->trig);
 96
 97	return IRQ_HANDLED;
 98}
 99
100static const struct iio_buffer_setup_ops iio_simple_dummy_buffer_setup_ops = {
101};
102
103int iio_simple_dummy_configure_buffer(struct iio_dev *indio_dev)
104{
105	return iio_triggered_buffer_setup(indio_dev, NULL,
106					  iio_simple_dummy_trigger_h,
107					  &iio_simple_dummy_buffer_setup_ops);
108}
109
110/**
111 * iio_simple_dummy_unconfigure_buffer() - release buffer resources
112 * @indio_dev: device instance state
113 */
114void iio_simple_dummy_unconfigure_buffer(struct iio_dev *indio_dev)
115{
116	iio_triggered_buffer_cleanup(indio_dev);
117}