aboutsummaryrefslogtreecommitdiff
path: root/drivers/input/misc/rotary_encoder.c
blob: 2be21694fac1bf1f66a6189cbd6ea96844a75c28 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
/*
 * rotary_encoder.c
 *
 * (c) 2009 Daniel Mack <daniel@caiaq.de>
 * Copyright (C) 2011 Johan Hovold <jhovold@gmail.com>
 *
 * state machine code inspired by code from Tim Ruetz
 *
 * A generic driver for rotary encoders connected to GPIO lines.
 * See file:Documentation/input/rotary-encoder.txt for more information
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/input.h>
#include <linux/device.h>
#include <linux/platform_device.h>
#include <linux/gpio.h>
#include <linux/rotary_encoder.h>
#include <linux/slab.h>

#define DRV_NAME "rotary-encoder"

struct rotary_encoder {
	struct input_dev *input;
	struct rotary_encoder_platform_data *pdata;

	unsigned int axis;
	unsigned int pos;

	unsigned int irq_a;
	unsigned int irq_b;

	bool armed;
	unsigned char dir;	/* 0 - clockwise, 1 - CCW */

	char last_stable;
};

static int rotary_encoder_get_state(struct rotary_encoder_platform_data *pdata)
{
	int a = !!gpio_get_value(pdata->gpio_a);
	int b = !!gpio_get_value(pdata->gpio_b);

	a ^= pdata->inverted_a;
	b ^= pdata->inverted_b;

	return ((a << 1) | b);
}

static void rotary_encoder_report_event(struct rotary_encoder *encoder)
{
	struct rotary_encoder_platform_data *pdata = encoder->pdata;

	if (pdata->relative_axis) {
		input_report_rel(encoder->input,
				 pdata->axis, encoder->dir ? -1 : 1);
	} else {
		unsigned int pos = encoder->pos;

		if (encoder->dir) {
			/* turning counter-clockwise */
			if (pdata->rollover)
				pos += pdata->steps;
			if (pos)
				pos--;
		} else {
			/* turning clockwise */
			if (pdata->rollover || pos < pdata->steps)
				pos++;
		}

		if (pdata->rollover)
			pos %= pdata->steps;

		encoder->pos = pos;
		input_report_abs(encoder->input, pdata->axis, encoder->pos);
	}

	input_sync(encoder->input);
}

static irqreturn_t rotary_encoder_irq(int irq, void *dev_id)
{
	struct rotary_encoder *encoder = dev_id;
	int state;

	state = rotary_encoder_get_state(encoder->pdata);

	switch (state) {
	case 0x0:
		if (encoder->armed) {
			rotary_encoder_report_event(encoder);
			encoder->armed = false;
		}
		break;

	case 0x1:
	case 0x2:
		if (encoder->armed)
			encoder->dir = state - 1;
		break;

	case 0x3:
		encoder->armed = true;
		break;
	}

	return IRQ_HANDLED;
}

static irqreturn_t rotary_encoder_half_period_irq(int irq, void *dev_id)
{
	struct rotary_encoder *encoder = dev_id;
	int state;

	state = rotary_encoder_get_state(encoder->pdata);

	switch (state) {
	case 0x00:
	case 0x03:
		if (state != encoder->last_stable) {
			rotary_encoder_report_event(encoder);
			encoder->last_stable = state;
		}
		break;

	case 0x01:
	case 0x02:
		encoder->dir = (encoder->last_stable + state) & 0x01;
		break;
	}

	return IRQ_HANDLED;
}

static int __devinit rotary_encoder_probe(struct platform_device *pdev)
{
	struct rotary_encoder_platform_data *pdata = pdev->dev.platform_data;
	struct rotary_encoder *encoder;
	struct input_dev *input;
	irq_handler_t handler;
	int err;

	if (!pdata) {
		dev_err(&pdev->dev, "missing platform data\n");
		return -ENOENT;
	}

	encoder = kzalloc(sizeof(struct rotary_encoder), GFP_KERNEL);
	input = input_allocate_device();
	if (!encoder || !input) {
		dev_err(&pdev->dev, "failed to allocate memory for device\n");
		err = -ENOMEM;
		goto exit_free_mem;
	}

	encoder->input = input;
	encoder->pdata = pdata;
	encoder->irq_a = gpio_to_irq(pdata->gpio_a);
	encoder->irq_b = gpio_to_irq(pdata->gpio_b);

	/* create and register the input driver */
	input->name = pdev->name;
	input->id.bustype = BUS_HOST;
	input->dev.parent = &pdev->dev;

	if (pdata->relative_axis) {
		input->evbit[0] = BIT_MASK(EV_REL);
		input->relbit[0] = BIT_MASK(pdata->axis);
	} else {
		input->evbit[0] = BIT_MASK(EV_ABS);
		input_set_abs_params(encoder->input,
				     pdata->axis, 0, pdata->steps, 0, 1);
	}

	err = input_register_device(input);
	if (err) {
		dev_err(&pdev->dev, "failed to register input device\n");
		goto exit_free_mem;
	}

	/* request the GPIOs */
	err = gpio_request(pdata->gpio_a, DRV_NAME);
	if (err) {
		dev_err(&pdev->dev, "unable to request GPIO %d\n",
			pdata->gpio_a);
		goto exit_unregister_input;
	}

	err = gpio_direction_input(pdata->gpio_a);
	if (err) {
		dev_err(&pdev->dev, "unable to set GPIO %d for input\n",
			pdata->gpio_a);
		goto exit_unregister_input;
	}

	err = gpio_request(pdata->gpio_b, DRV_NAME);
	if (err) {
		dev_err(&pdev->dev, "unable to request GPIO %d\n",
			pdata->gpio_b);
		goto exit_free_gpio_a;
	}

	err = gpio_direction_input(pdata->gpio_b);
	if (err) {
		dev_err(&pdev->dev, "unable to set GPIO %d for input\n",
			pdata->gpio_b);
		goto exit_free_gpio_a;
	}

	/* request the IRQs */
	if (pdata->half_period) {
		handler = &rotary_encoder_half_period_irq;
		encoder->last_stable = rotary_encoder_get_state(pdata);
	} else {
		handler = &rotary_encoder_irq;
	}

	err = request_irq(encoder->irq_a, handler,
			  IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING,
			  DRV_NAME, encoder);
	if (err) {
		dev_err(&pdev->dev, "unable to request IRQ %d\n",
			encoder->irq_a);
		goto exit_free_gpio_b;
	}

	err = request_irq(encoder->irq_b, handler,
			  IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING,
			  DRV_NAME, encoder);
	if (err) {
		dev_err(&pdev->dev, "unable to request IRQ %d\n",
			encoder->irq_b);
		goto exit_free_irq_a;
	}

	platform_set_drvdata(pdev, encoder);

	return 0;

exit_free_irq_a:
	free_irq(encoder->irq_a, encoder);
exit_free_gpio_b:
	gpio_free(pdata->gpio_b);
exit_free_gpio_a:
	gpio_free(pdata->gpio_a);
exit_unregister_input:
	input_unregister_device(input);
	input = NULL; /* so we don't try to free it */
exit_free_mem:
	input_free_device(input);
	kfree(encoder);
	return err;
}

static int __devexit rotary_encoder_remove(struct platform_device *pdev)
{
	struct rotary_encoder *encoder = platform_get_drvdata(pdev);
	struct rotary_encoder_platform_data *pdata = pdev->dev.platform_data;

	free_irq(encoder->irq_a, encoder);
	free_irq(encoder->irq_b, encoder);
	gpio_free(pdata->gpio_a);
	gpio_free(pdata->gpio_b);
	input_unregister_device(encoder->input);
	platform_set_drvdata(pdev, NULL);
	kfree(encoder);

	return 0;
}

static struct platform_driver rotary_encoder_driver = {
	.probe		= rotary_encoder_probe,
	.remove		= __devexit_p(rotary_encoder_remove),
	.driver		= {
		.name	= DRV_NAME,
		.owner	= THIS_MODULE,
	}
};

static int __init rotary_encoder_init(void)
{
	return platform_driver_register(&rotary_encoder_driver);
}

static void __exit rotary_encoder_exit(void)
{
	platform_driver_unregister(&rotary_encoder_driver);
}

module_init(rotary_encoder_init);
module_exit(rotary_encoder_exit);

MODULE_ALIAS("platform:" DRV_NAME);
MODULE_DESCRIPTION("GPIO rotary encoder driver");
MODULE_AUTHOR("Daniel Mack <daniel@caiaq.de>, Johan Hovold");
MODULE_LICENSE("GPL v2");