1 /*
2 * Copyright 2016 Jonathan Cameron <jic23@kernel.org>
3 *
4 * Licensed under the GPL-2.
5 *
6 * Based on a mashup of the hrtimer trigger and continuous sampling proposal of
7 * Gregor Boirie <gregor.boirie@parrot.com>
8 *
9 * Note this is still rather experimental and may eat babies.
10 *
11 * Todo
12 * * Protect against connection of devices that 'need' the top half
13 * handler.
14 * * Work out how to run top half handlers in this context if it is
15 * safe to do so (timestamp grabbing for example)
16 *
17 * Tested against a max1363. Used about 33% cpu for the thread and 20%
18 * for generic_buffer piping to /dev/null. Watermark set at 64 on a 128
19 * element kfifo buffer.
20 */
21
22 #include <linux/kernel.h>
23 #include <linux/module.h>
24 #include <linux/platform_device.h>
25 #include <linux/slab.h>
26 #include <linux/irq_work.h>
27 #include <linux/kthread.h>
28 #include <linux/freezer.h>
29
30 #include <linux/iio/iio.h>
31 #include <linux/iio/trigger.h>
32 #include <linux/iio/sw_trigger.h>
33
34 struct iio_loop_info {
35 struct iio_sw_trigger swt;
36 struct task_struct *task;
37 };
38
39 static struct config_item_type iio_loop_type = {
40 .ct_owner = THIS_MODULE,
41 };
42
iio_loop_thread(void * data)43 static int iio_loop_thread(void *data)
44 {
45 struct iio_trigger *trig = data;
46
47 set_freezable();
48
49 do {
50 iio_trigger_poll_chained(trig);
51 } while (likely(!kthread_freezable_should_stop(NULL)));
52
53 return 0;
54 }
55
iio_loop_trigger_set_state(struct iio_trigger * trig,bool state)56 static int iio_loop_trigger_set_state(struct iio_trigger *trig, bool state)
57 {
58 struct iio_loop_info *loop_trig = iio_trigger_get_drvdata(trig);
59
60 if (state) {
61 loop_trig->task = kthread_run(iio_loop_thread,
62 trig, trig->name);
63 if (unlikely(IS_ERR(loop_trig->task))) {
64 dev_err(&trig->dev,
65 "failed to create trigger loop thread\n");
66 return PTR_ERR(loop_trig->task);
67 }
68 } else {
69 kthread_stop(loop_trig->task);
70 }
71
72 return 0;
73 }
74
75 static const struct iio_trigger_ops iio_loop_trigger_ops = {
76 .set_trigger_state = iio_loop_trigger_set_state,
77 .owner = THIS_MODULE,
78 };
79
iio_trig_loop_probe(const char * name)80 static struct iio_sw_trigger *iio_trig_loop_probe(const char *name)
81 {
82 struct iio_loop_info *trig_info;
83 int ret;
84
85 trig_info = kzalloc(sizeof(*trig_info), GFP_KERNEL);
86 if (!trig_info)
87 return ERR_PTR(-ENOMEM);
88
89 trig_info->swt.trigger = iio_trigger_alloc("%s", name);
90 if (!trig_info->swt.trigger) {
91 ret = -ENOMEM;
92 goto err_free_trig_info;
93 }
94
95 iio_trigger_set_drvdata(trig_info->swt.trigger, trig_info);
96 trig_info->swt.trigger->ops = &iio_loop_trigger_ops;
97
98 ret = iio_trigger_register(trig_info->swt.trigger);
99 if (ret)
100 goto err_free_trigger;
101
102 iio_swt_group_init_type_name(&trig_info->swt, name, &iio_loop_type);
103
104 return &trig_info->swt;
105
106 err_free_trigger:
107 iio_trigger_free(trig_info->swt.trigger);
108 err_free_trig_info:
109 kfree(trig_info);
110
111 return ERR_PTR(ret);
112 }
113
iio_trig_loop_remove(struct iio_sw_trigger * swt)114 static int iio_trig_loop_remove(struct iio_sw_trigger *swt)
115 {
116 struct iio_loop_info *trig_info;
117
118 trig_info = iio_trigger_get_drvdata(swt->trigger);
119
120 iio_trigger_unregister(swt->trigger);
121 iio_trigger_free(swt->trigger);
122 kfree(trig_info);
123
124 return 0;
125 }
126
127 static const struct iio_sw_trigger_ops iio_trig_loop_ops = {
128 .probe = iio_trig_loop_probe,
129 .remove = iio_trig_loop_remove,
130 };
131
132 static struct iio_sw_trigger_type iio_trig_loop = {
133 .name = "loop",
134 .owner = THIS_MODULE,
135 .ops = &iio_trig_loop_ops,
136 };
137
138 module_iio_sw_trigger_driver(iio_trig_loop);
139
140 MODULE_AUTHOR("Jonathan Cameron <jic23@kernel.org>");
141 MODULE_DESCRIPTION("Loop based trigger for the iio subsystem");
142 MODULE_LICENSE("GPL v2");
143 MODULE_ALIAS("platform:iio-trig-loop");
144