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 
32 struct 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 
48 static 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 
59 static 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 
91 static 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 
120 static 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
146 static const struct of_device_id rotary_encoder_of_match[] = {
147 	{ .compatible = "rotary-encoder", },
148 	{ },
149 };
150 MODULE_DEVICE_TABLE(of, rotary_encoder_of_match);
151 
152 static 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
187 static inline struct rotary_encoder_platform_data *
188 rotary_encoder_parse_dt(struct device *dev)
189 {
190 	return NULL;
191 }
192 #endif
193 
194 static 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 
287 exit_free_irq_b:
288 	free_irq(encoder->irq_b, encoder);
289 exit_free_irq_a:
290 	free_irq(encoder->irq_a, encoder);
291 exit_free_gpio_b:
292 	gpio_free(pdata->gpio_b);
293 exit_free_gpio_a:
294 	gpio_free(pdata->gpio_a);
295 exit_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 
304 static 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 
323 static struct platform_driver rotary_encoder_driver = {
324 	.probe		= rotary_encoder_probe,
325 	.remove		= rotary_encoder_remove,
326 	.driver		= {
327 		.name	= DRV_NAME,
328 		.owner	= THIS_MODULE,
329 		.of_match_table = of_match_ptr(rotary_encoder_of_match),
330 	}
331 };
332 module_platform_driver(rotary_encoder_driver);
333 
334 MODULE_ALIAS("platform:" DRV_NAME);
335 MODULE_DESCRIPTION("GPIO rotary encoder driver");
336 MODULE_AUTHOR("Daniel Mack <daniel@caiaq.de>, Johan Hovold");
337 MODULE_LICENSE("GPL v2");
338