1/*
2 * rotary_encoder.c
3 *
4 * (c) 2009 Daniel Mack <daniel@caiaq.de>
5 * Copyright (C) 2011 Johan Hovold <jhovold@gmail.com>
6 *
7 * state machine code inspired by code from Tim Ruetz
8 *
9 * A generic driver for rotary encoders connected to GPIO lines.
10 * See file:Documentation/input/rotary-encoder.txt for more information
11 *
12 * This program is free software; you can redistribute it and/or modify
13 * it under the terms of the GNU General Public License version 2 as
14 * published by the Free Software Foundation.
15 */
16
17#include <linux/kernel.h>
18#include <linux/module.h>
19#include <linux/interrupt.h>
20#include <linux/input.h>
21#include <linux/device.h>
22#include <linux/platform_device.h>
23#include <linux/gpio.h>
24#include <linux/rotary_encoder.h>
25#include <linux/slab.h>
26#include <linux/of.h>
27#include <linux/of_platform.h>
28#include <linux/of_gpio.h>
29
30#define DRV_NAME "rotary-encoder"
31
32struct rotary_encoder {
33	struct input_dev *input;
34	const struct rotary_encoder_platform_data *pdata;
35
36	unsigned int axis;
37	unsigned int pos;
38
39	unsigned int irq_a;
40	unsigned int irq_b;
41
42	bool armed;
43	unsigned char dir;	/* 0 - clockwise, 1 - CCW */
44
45	char last_stable;
46};
47
48static int rotary_encoder_get_state(const struct rotary_encoder_platform_data *pdata)
49{
50	int a = !!gpio_get_value(pdata->gpio_a);
51	int b = !!gpio_get_value(pdata->gpio_b);
52
53	a ^= pdata->inverted_a;
54	b ^= pdata->inverted_b;
55
56	return ((a << 1) | b);
57}
58
59static void rotary_encoder_report_event(struct rotary_encoder *encoder)
60{
61	const struct rotary_encoder_platform_data *pdata = encoder->pdata;
62
63	if (pdata->relative_axis) {
64		input_report_rel(encoder->input,
65				 pdata->axis, encoder->dir ? -1 : 1);
66	} else {
67		unsigned int pos = encoder->pos;
68
69		if (encoder->dir) {
70			/* turning counter-clockwise */
71			if (pdata->rollover)
72				pos += pdata->steps;
73			if (pos)
74				pos--;
75		} else {
76			/* turning clockwise */
77			if (pdata->rollover || pos < pdata->steps)
78				pos++;
79		}
80
81		if (pdata->rollover)
82			pos %= pdata->steps;
83
84		encoder->pos = pos;
85		input_report_abs(encoder->input, pdata->axis, encoder->pos);
86	}
87
88	input_sync(encoder->input);
89}
90
91static irqreturn_t rotary_encoder_irq(int irq, void *dev_id)
92{
93	struct rotary_encoder *encoder = dev_id;
94	int state;
95
96	state = rotary_encoder_get_state(encoder->pdata);
97
98	switch (state) {
99	case 0x0:
100		if (encoder->armed) {
101			rotary_encoder_report_event(encoder);
102			encoder->armed = false;
103		}
104		break;
105
106	case 0x1:
107	case 0x2:
108		if (encoder->armed)
109			encoder->dir = state - 1;
110		break;
111
112	case 0x3:
113		encoder->armed = true;
114		break;
115	}
116
117	return IRQ_HANDLED;
118}
119
120static irqreturn_t rotary_encoder_half_period_irq(int irq, void *dev_id)
121{
122	struct rotary_encoder *encoder = dev_id;
123	int state;
124
125	state = rotary_encoder_get_state(encoder->pdata);
126
127	switch (state) {
128	case 0x00:
129	case 0x03:
130		if (state != encoder->last_stable) {
131			rotary_encoder_report_event(encoder);
132			encoder->last_stable = state;
133		}
134		break;
135
136	case 0x01:
137	case 0x02:
138		encoder->dir = (encoder->last_stable + state) & 0x01;
139		break;
140	}
141
142	return IRQ_HANDLED;
143}
144
145#ifdef CONFIG_OF
146static const struct of_device_id rotary_encoder_of_match[] = {
147	{ .compatible = "rotary-encoder", },
148	{ },
149};
150MODULE_DEVICE_TABLE(of, rotary_encoder_of_match);
151
152static struct rotary_encoder_platform_data *rotary_encoder_parse_dt(struct device *dev)
153{
154	const struct of_device_id *of_id =
155				of_match_device(rotary_encoder_of_match, dev);
156	struct device_node *np = dev->of_node;
157	struct rotary_encoder_platform_data *pdata;
158	enum of_gpio_flags flags;
159
160	if (!of_id || !np)
161		return NULL;
162
163	pdata = kzalloc(sizeof(struct rotary_encoder_platform_data),
164			GFP_KERNEL);
165	if (!pdata)
166		return ERR_PTR(-ENOMEM);
167
168	of_property_read_u32(np, "rotary-encoder,steps", &pdata->steps);
169	of_property_read_u32(np, "linux,axis", &pdata->axis);
170
171	pdata->gpio_a = of_get_gpio_flags(np, 0, &flags);
172	pdata->inverted_a = flags & OF_GPIO_ACTIVE_LOW;
173
174	pdata->gpio_b = of_get_gpio_flags(np, 1, &flags);
175	pdata->inverted_b = flags & OF_GPIO_ACTIVE_LOW;
176
177	pdata->relative_axis = !!of_get_property(np,
178					"rotary-encoder,relative-axis", NULL);
179	pdata->rollover = !!of_get_property(np,
180					"rotary-encoder,rollover", NULL);
181	pdata->half_period = !!of_get_property(np,
182					"rotary-encoder,half-period", NULL);
183
184	return pdata;
185}
186#else
187static inline struct rotary_encoder_platform_data *
188rotary_encoder_parse_dt(struct device *dev)
189{
190	return NULL;
191}
192#endif
193
194static int rotary_encoder_probe(struct platform_device *pdev)
195{
196	struct device *dev = &pdev->dev;
197	const struct rotary_encoder_platform_data *pdata = dev_get_platdata(dev);
198	struct rotary_encoder *encoder;
199	struct input_dev *input;
200	irq_handler_t handler;
201	int err;
202
203	if (!pdata) {
204		pdata = rotary_encoder_parse_dt(dev);
205		if (IS_ERR(pdata))
206			return PTR_ERR(pdata);
207
208		if (!pdata) {
209			dev_err(dev, "missing platform data\n");
210			return -EINVAL;
211		}
212	}
213
214	encoder = kzalloc(sizeof(struct rotary_encoder), GFP_KERNEL);
215	input = input_allocate_device();
216	if (!encoder || !input) {
217		err = -ENOMEM;
218		goto exit_free_mem;
219	}
220
221	encoder->input = input;
222	encoder->pdata = pdata;
223
224	input->name = pdev->name;
225	input->id.bustype = BUS_HOST;
226	input->dev.parent = dev;
227
228	if (pdata->relative_axis) {
229		input->evbit[0] = BIT_MASK(EV_REL);
230		input->relbit[0] = BIT_MASK(pdata->axis);
231	} else {
232		input->evbit[0] = BIT_MASK(EV_ABS);
233		input_set_abs_params(encoder->input,
234				     pdata->axis, 0, pdata->steps, 0, 1);
235	}
236
237	/* request the GPIOs */
238	err = gpio_request_one(pdata->gpio_a, GPIOF_IN, dev_name(dev));
239	if (err) {
240		dev_err(dev, "unable to request GPIO %d\n", pdata->gpio_a);
241		goto exit_free_mem;
242	}
243
244	err = gpio_request_one(pdata->gpio_b, GPIOF_IN, dev_name(dev));
245	if (err) {
246		dev_err(dev, "unable to request GPIO %d\n", pdata->gpio_b);
247		goto exit_free_gpio_a;
248	}
249
250	encoder->irq_a = gpio_to_irq(pdata->gpio_a);
251	encoder->irq_b = gpio_to_irq(pdata->gpio_b);
252
253	/* request the IRQs */
254	if (pdata->half_period) {
255		handler = &rotary_encoder_half_period_irq;
256		encoder->last_stable = rotary_encoder_get_state(pdata);
257	} else {
258		handler = &rotary_encoder_irq;
259	}
260
261	err = request_irq(encoder->irq_a, handler,
262			  IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING,
263			  DRV_NAME, encoder);
264	if (err) {
265		dev_err(dev, "unable to request IRQ %d\n", encoder->irq_a);
266		goto exit_free_gpio_b;
267	}
268
269	err = request_irq(encoder->irq_b, handler,
270			  IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING,
271			  DRV_NAME, encoder);
272	if (err) {
273		dev_err(dev, "unable to request IRQ %d\n", encoder->irq_b);
274		goto exit_free_irq_a;
275	}
276
277	err = input_register_device(input);
278	if (err) {
279		dev_err(dev, "failed to register input device\n");
280		goto exit_free_irq_b;
281	}
282
283	platform_set_drvdata(pdev, encoder);
284
285	return 0;
286
287exit_free_irq_b:
288	free_irq(encoder->irq_b, encoder);
289exit_free_irq_a:
290	free_irq(encoder->irq_a, encoder);
291exit_free_gpio_b:
292	gpio_free(pdata->gpio_b);
293exit_free_gpio_a:
294	gpio_free(pdata->gpio_a);
295exit_free_mem:
296	input_free_device(input);
297	kfree(encoder);
298	if (!dev_get_platdata(&pdev->dev))
299		kfree(pdata);
300
301	return err;
302}
303
304static int rotary_encoder_remove(struct platform_device *pdev)
305{
306	struct rotary_encoder *encoder = platform_get_drvdata(pdev);
307	const struct rotary_encoder_platform_data *pdata = encoder->pdata;
308
309	free_irq(encoder->irq_a, encoder);
310	free_irq(encoder->irq_b, encoder);
311	gpio_free(pdata->gpio_a);
312	gpio_free(pdata->gpio_b);
313
314	input_unregister_device(encoder->input);
315	kfree(encoder);
316
317	if (!dev_get_platdata(&pdev->dev))
318		kfree(pdata);
319
320	return 0;
321}
322
323static struct platform_driver rotary_encoder_driver = {
324	.probe		= rotary_encoder_probe,
325	.remove		= rotary_encoder_remove,
326	.driver		= {
327		.name	= DRV_NAME,
328		.of_match_table = of_match_ptr(rotary_encoder_of_match),
329	}
330};
331module_platform_driver(rotary_encoder_driver);
332
333MODULE_ALIAS("platform:" DRV_NAME);
334MODULE_DESCRIPTION("GPIO rotary encoder driver");
335MODULE_AUTHOR("Daniel Mack <daniel@caiaq.de>, Johan Hovold");
336MODULE_LICENSE("GPL v2");
337