1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Copyright 2016 Jonathan Cameron <jic23@kernel.org>
4 *
5 * Based on a mashup of the hrtimer trigger and continuous sampling proposal of
6 * Gregor Boirie <gregor.boirie@parrot.com>
7 *
8 * Note this is still rather experimental and may eat babies.
9 *
10 * Todo
11 * * Protect against connection of devices that 'need' the top half
12 *   handler.
13 * * Work out how to run top half handlers in this context if it is
14 *   safe to do so (timestamp grabbing for example)
15 *
16 * Tested against a max1363. Used about 33% cpu for the thread and 20%
17 * for generic_buffer piping to /dev/null. Watermark set at 64 on a 128
18 * element kfifo buffer.
19 */
20
21#include <linux/kernel.h>
22#include <linux/module.h>
23#include <linux/platform_device.h>
24#include <linux/slab.h>
25#include <linux/irq_work.h>
26#include <linux/kthread.h>
27#include <linux/freezer.h>
28
29#include <linux/iio/iio.h>
30#include <linux/iio/trigger.h>
31#include <linux/iio/sw_trigger.h>
32
33struct iio_loop_info {
34	struct iio_sw_trigger swt;
35	struct task_struct *task;
36};
37
38static const struct config_item_type iio_loop_type = {
39	.ct_owner = THIS_MODULE,
40};
41
42static int iio_loop_thread(void *data)
43{
44	struct iio_trigger *trig = data;
45
46	set_freezable();
47
48	do {
49		iio_trigger_poll_nested(trig);
50	} while (likely(!kthread_freezable_should_stop(NULL)));
51
52	return 0;
53}
54
55static int iio_loop_trigger_set_state(struct iio_trigger *trig, bool state)
56{
57	struct iio_loop_info *loop_trig = iio_trigger_get_drvdata(trig);
58
59	if (state) {
60		loop_trig->task = kthread_run(iio_loop_thread,
61					      trig, trig->name);
62		if (IS_ERR(loop_trig->task)) {
63			dev_err(&trig->dev,
64				"failed to create trigger loop thread\n");
65			return PTR_ERR(loop_trig->task);
66		}
67	} else {
68		kthread_stop(loop_trig->task);
69	}
70
71	return 0;
72}
73
74static const struct iio_trigger_ops iio_loop_trigger_ops = {
75	.set_trigger_state = iio_loop_trigger_set_state,
76};
77
78static struct iio_sw_trigger *iio_trig_loop_probe(const char *name)
79{
80	struct iio_loop_info *trig_info;
81	int ret;
82
83	trig_info = kzalloc(sizeof(*trig_info), GFP_KERNEL);
84	if (!trig_info)
85		return ERR_PTR(-ENOMEM);
86
87	trig_info->swt.trigger = iio_trigger_alloc(NULL, "%s", name);
88	if (!trig_info->swt.trigger) {
89		ret = -ENOMEM;
90		goto err_free_trig_info;
91	}
92
93	iio_trigger_set_drvdata(trig_info->swt.trigger, trig_info);
94	trig_info->swt.trigger->ops = &iio_loop_trigger_ops;
95
96	ret = iio_trigger_register(trig_info->swt.trigger);
97	if (ret)
98		goto err_free_trigger;
99
100	iio_swt_group_init_type_name(&trig_info->swt, name, &iio_loop_type);
101
102	return &trig_info->swt;
103
104err_free_trigger:
105	iio_trigger_free(trig_info->swt.trigger);
106err_free_trig_info:
107	kfree(trig_info);
108
109	return ERR_PTR(ret);
110}
111
112static int iio_trig_loop_remove(struct iio_sw_trigger *swt)
113{
114	struct iio_loop_info *trig_info;
115
116	trig_info = iio_trigger_get_drvdata(swt->trigger);
117
118	iio_trigger_unregister(swt->trigger);
119	iio_trigger_free(swt->trigger);
120	kfree(trig_info);
121
122	return 0;
123}
124
125static const struct iio_sw_trigger_ops iio_trig_loop_ops = {
126	.probe = iio_trig_loop_probe,
127	.remove = iio_trig_loop_remove,
128};
129
130static struct iio_sw_trigger_type iio_trig_loop = {
131	.name = "loop",
132	.owner = THIS_MODULE,
133	.ops = &iio_trig_loop_ops,
134};
135
136module_iio_sw_trigger_driver(iio_trig_loop);
137
138MODULE_AUTHOR("Jonathan Cameron <jic23@kernel.org>");
139MODULE_DESCRIPTION("Loop based trigger for the iio subsystem");
140MODULE_LICENSE("GPL v2");
141MODULE_ALIAS("platform:iio-trig-loop");
142