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 
33 struct iio_loop_info {
34 	struct iio_sw_trigger swt;
35 	struct task_struct *task;
36 };
37 
38 static const struct config_item_type iio_loop_type = {
39 	.ct_owner = THIS_MODULE,
40 };
41 
42 static int iio_loop_thread(void *data)
43 {
44 	struct iio_trigger *trig = data;
45 
46 	set_freezable();
47 
48 	do {
49 		iio_trigger_poll_chained(trig);
50 	} while (likely(!kthread_freezable_should_stop(NULL)));
51 
52 	return 0;
53 }
54 
55 static 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 
74 static const struct iio_trigger_ops iio_loop_trigger_ops = {
75 	.set_trigger_state = iio_loop_trigger_set_state,
76 };
77 
78 static 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 
104 err_free_trigger:
105 	iio_trigger_free(trig_info->swt.trigger);
106 err_free_trig_info:
107 	kfree(trig_info);
108 
109 	return ERR_PTR(ret);
110 }
111 
112 static 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 
125 static const struct iio_sw_trigger_ops iio_trig_loop_ops = {
126 	.probe = iio_trig_loop_probe,
127 	.remove = iio_trig_loop_remove,
128 };
129 
130 static struct iio_sw_trigger_type iio_trig_loop = {
131 	.name = "loop",
132 	.owner = THIS_MODULE,
133 	.ops = &iio_trig_loop_ops,
134 };
135 
136 module_iio_sw_trigger_driver(iio_trig_loop);
137 
138 MODULE_AUTHOR("Jonathan Cameron <jic23@kernel.org>");
139 MODULE_DESCRIPTION("Loop based trigger for the iio subsystem");
140 MODULE_LICENSE("GPL v2");
141 MODULE_ALIAS("platform:iio-trig-loop");
142