timed_gpio.c revision 07960058f0ce77ddc3027d3e45a5de1fb977334f 
1/* drivers/misc/timed_gpio.c
2 *
3 * Copyright (C) 2008 Google, Inc.
4 * Author: Mike Lockwood <lockwood@android.com>
5 *
6 * This software is licensed under the terms of the GNU General Public
7 * License version 2, as published by the Free Software Foundation, and
8 * may be copied, distributed, and modified under those terms.
9 *
10 * This program is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
13 * GNU General Public License for more details.
14 *
15 */
16
17#include <linux/module.h>
18#include <linux/platform_device.h>
19#include <linux/hrtimer.h>
20#include <linux/err.h>
21#include <linux/gpio.h>
22
23#include "timed_gpio.h"
24
25
26static struct class *timed_gpio_class;
27
28struct timed_gpio_data {
29	struct device *dev;
30	struct hrtimer timer;
31	spinlock_t lock;
32	unsigned 	gpio;
33	int 		max_timeout;
34	u8 		active_low;
35};
36
37static enum hrtimer_restart gpio_timer_func(struct hrtimer *timer)
38{
39	struct timed_gpio_data *gpio_data = container_of(timer, struct timed_gpio_data, timer);
40
41	gpio_direction_output(gpio_data->gpio, gpio_data->active_low ? 1 : 0);
42	return HRTIMER_NORESTART;
43}
44
45static ssize_t gpio_enable_show(struct device *dev, struct device_attribute *attr, char *buf)
46{
47	struct timed_gpio_data *gpio_data = dev_get_drvdata(dev);
48	int remaining;
49
50	if (hrtimer_active(&gpio_data->timer)) {
51		ktime_t r = hrtimer_get_remaining(&gpio_data->timer);
52		struct timeval t = ktime_to_timeval(r);
53		remaining = t.tv_sec * 1000 + t.tv_usec;
54	} else
55		remaining = 0;
56
57	return sprintf(buf, "%d\n", remaining);
58}
59
60static ssize_t gpio_enable_store(
61		struct device *dev, struct device_attribute *attr,
62		const char *buf, size_t size)
63{
64	struct timed_gpio_data *gpio_data = dev_get_drvdata(dev);
65	int value;
66	unsigned long	flags;
67
68	sscanf(buf, "%d", &value);
69
70	spin_lock_irqsave(&gpio_data->lock, flags);
71
72	/* cancel previous timer and set GPIO according to value */
73	hrtimer_cancel(&gpio_data->timer);
74	gpio_direction_output(gpio_data->gpio, gpio_data->active_low ? !value : !!value);
75
76	if (value > 0) {
77		if (value > gpio_data->max_timeout)
78			value = gpio_data->max_timeout;
79
80		hrtimer_start(&gpio_data->timer,
81						ktime_set(value / 1000, (value % 1000) * 1000000),
82						HRTIMER_MODE_REL);
83	}
84
85	spin_unlock_irqrestore(&gpio_data->lock, flags);
86
87	return size;
88}
89
90static DEVICE_ATTR(enable, S_IRUGO | S_IWUSR, gpio_enable_show, gpio_enable_store);
91
92static int timed_gpio_probe(struct platform_device *pdev)
93{
94	struct timed_gpio_platform_data *pdata = pdev->dev.platform_data;
95	struct timed_gpio *cur_gpio;
96	struct timed_gpio_data *gpio_data, *gpio_dat;
97	int i, ret = 0;
98
99	if (!pdata)
100		return -EBUSY;
101
102	gpio_data = kzalloc(sizeof(struct timed_gpio_data) * pdata->num_gpios, GFP_KERNEL);
103	if (!gpio_data)
104		return -ENOMEM;
105
106	for (i = 0; i < pdata->num_gpios; i++) {
107		cur_gpio = &pdata->gpios[i];
108		gpio_dat = &gpio_data[i];
109
110		hrtimer_init(&gpio_dat->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
111		gpio_dat->timer.function = gpio_timer_func;
112		spin_lock_init(&gpio_dat->lock);
113
114		gpio_dat->gpio = cur_gpio->gpio;
115		gpio_dat->max_timeout = cur_gpio->max_timeout;
116		gpio_dat->active_low = cur_gpio->active_low;
117		gpio_direction_output(gpio_dat->gpio, gpio_dat->active_low);
118
119		gpio_dat->dev = device_create(timed_gpio_class, &pdev->dev, 0, "%s", cur_gpio->name);
120		if (unlikely(IS_ERR(gpio_dat->dev)))
121			return PTR_ERR(gpio_dat->dev);
122
123		dev_set_drvdata(gpio_dat->dev, gpio_dat);
124		ret = device_create_file(gpio_dat->dev, &dev_attr_enable);
125		if (ret)
126			return ret;
127	}
128
129	platform_set_drvdata(pdev, gpio_data);
130
131	return 0;
132}
133
134static int timed_gpio_remove(struct platform_device *pdev)
135{
136	struct timed_gpio_platform_data *pdata = pdev->dev.platform_data;
137	struct timed_gpio_data *gpio_data = platform_get_drvdata(pdev);
138	int i;
139
140	for (i = 0; i < pdata->num_gpios; i++) {
141		device_remove_file(gpio_data[i].dev, &dev_attr_enable);
142		device_unregister(gpio_data[i].dev);
143	}
144
145	kfree(gpio_data);
146
147	return 0;
148}
149
150static struct platform_driver timed_gpio_driver = {
151	.probe		= timed_gpio_probe,
152	.remove		= timed_gpio_remove,
153	.driver		= {
154		.name		= "timed-gpio",
155		.owner		= THIS_MODULE,
156	},
157};
158
159static int __init timed_gpio_init(void)
160{
161	timed_gpio_class = class_create(THIS_MODULE, "timed_output");
162	if (IS_ERR(timed_gpio_class))
163		return PTR_ERR(timed_gpio_class);
164	return platform_driver_register(&timed_gpio_driver);
165}
166
167static void __exit timed_gpio_exit(void)
168{
169	class_destroy(timed_gpio_class);
170	platform_driver_unregister(&timed_gpio_driver);
171}
172
173module_init(timed_gpio_init);
174module_exit(timed_gpio_exit);
175
176MODULE_AUTHOR("Mike Lockwood <lockwood@android.com>");
177MODULE_DESCRIPTION("timed gpio driver");
178MODULE_LICENSE("GPL");
179