xref: /linux/drivers/input/misc/rotary_encoder.c (revision 0883c2c06fb5bcf5b9e008270827e63c09a88c1e) 
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/consumer.h>
24 #include <linux/slab.h>
25 #include <linux/of.h>
26 #include <linux/pm.h>
27 #include <linux/property.h>
28 
29 #define DRV_NAME "rotary-encoder"
30 
31 struct rotary_encoder {
32 	struct input_dev *input;
33 
34 	struct mutex access_mutex;
35 
36 	u32 steps;
37 	u32 axis;
38 	bool relative_axis;
39 	bool rollover;
40 
41 	unsigned int pos;
42 
43 	struct gpio_descs *gpios;
44 
45 	unsigned int *irq;
46 
47 	bool armed;
48 	signed char dir;	/* 1 - clockwise, -1 - CCW */
49 
50 	unsigned int last_stable;
51 };
52 
53 static unsigned int rotary_encoder_get_state(struct rotary_encoder *encoder)
54 {
55 	int i;
56 	unsigned int ret = 0;
57 
58 	for (i = 0; i < encoder->gpios->ndescs; ++i) {
59 		int val = gpiod_get_value_cansleep(encoder->gpios->desc[i]);
60 		/* convert from gray encoding to normal */
61 		if (ret & 1)
62 			val = !val;
63 
64 		ret = ret << 1 | val;
65 	}
66 
67 	return ret & 3;
68 }
69 
70 static void rotary_encoder_report_event(struct rotary_encoder *encoder)
71 {
72 	if (encoder->relative_axis) {
73 		input_report_rel(encoder->input,
74 				 encoder->axis, encoder->dir);
75 	} else {
76 		unsigned int pos = encoder->pos;
77 
78 		if (encoder->dir < 0) {
79 			/* turning counter-clockwise */
80 			if (encoder->rollover)
81 				pos += encoder->steps;
82 			if (pos)
83 				pos--;
84 		} else {
85 			/* turning clockwise */
86 			if (encoder->rollover || pos < encoder->steps)
87 				pos++;
88 		}
89 
90 		if (encoder->rollover)
91 			pos %= encoder->steps;
92 
93 		encoder->pos = pos;
94 		input_report_abs(encoder->input, encoder->axis, encoder->pos);
95 	}
96 
97 	input_sync(encoder->input);
98 }
99 
100 static irqreturn_t rotary_encoder_irq(int irq, void *dev_id)
101 {
102 	struct rotary_encoder *encoder = dev_id;
103 	unsigned int state;
104 
105 	mutex_lock(&encoder->access_mutex);
106 
107 	state = rotary_encoder_get_state(encoder);
108 
109 	switch (state) {
110 	case 0x0:
111 		if (encoder->armed) {
112 			rotary_encoder_report_event(encoder);
113 			encoder->armed = false;
114 		}
115 		break;
116 
117 	case 0x1:
118 	case 0x3:
119 		if (encoder->armed)
120 			encoder->dir = 2 - state;
121 		break;
122 
123 	case 0x2:
124 		encoder->armed = true;
125 		break;
126 	}
127 
128 	mutex_unlock(&encoder->access_mutex);
129 
130 	return IRQ_HANDLED;
131 }
132 
133 static irqreturn_t rotary_encoder_half_period_irq(int irq, void *dev_id)
134 {
135 	struct rotary_encoder *encoder = dev_id;
136 	unsigned int state;
137 
138 	mutex_lock(&encoder->access_mutex);
139 
140 	state = rotary_encoder_get_state(encoder);
141 
142 	if (state & 1) {
143 		encoder->dir = ((encoder->last_stable - state + 1) % 4) - 1;
144 	} else {
145 		if (state != encoder->last_stable) {
146 			rotary_encoder_report_event(encoder);
147 			encoder->last_stable = state;
148 		}
149 	}
150 
151 	mutex_unlock(&encoder->access_mutex);
152 
153 	return IRQ_HANDLED;
154 }
155 
156 static irqreturn_t rotary_encoder_quarter_period_irq(int irq, void *dev_id)
157 {
158 	struct rotary_encoder *encoder = dev_id;
159 	unsigned int state;
160 
161 	mutex_lock(&encoder->access_mutex);
162 
163 	state = rotary_encoder_get_state(encoder);
164 
165 	if ((encoder->last_stable + 1) % 4 == state)
166 		encoder->dir = 1;
167 	else if (encoder->last_stable == (state + 1) % 4)
168 		encoder->dir = -1;
169 	else
170 		goto out;
171 
172 	rotary_encoder_report_event(encoder);
173 
174 out:
175 	encoder->last_stable = state;
176 	mutex_unlock(&encoder->access_mutex);
177 
178 	return IRQ_HANDLED;
179 }
180 
181 static int rotary_encoder_probe(struct platform_device *pdev)
182 {
183 	struct device *dev = &pdev->dev;
184 	struct rotary_encoder *encoder;
185 	struct input_dev *input;
186 	irq_handler_t handler;
187 	u32 steps_per_period;
188 	unsigned int i;
189 	int err;
190 
191 	encoder = devm_kzalloc(dev, sizeof(struct rotary_encoder), GFP_KERNEL);
192 	if (!encoder)
193 		return -ENOMEM;
194 
195 	mutex_init(&encoder->access_mutex);
196 
197 	device_property_read_u32(dev, "rotary-encoder,steps", &encoder->steps);
198 
199 	err = device_property_read_u32(dev, "rotary-encoder,steps-per-period",
200 				       &steps_per_period);
201 	if (err) {
202 		/*
203 		 * The 'half-period' property has been deprecated, you must
204 		 * use 'steps-per-period' and set an appropriate value, but
205 		 * we still need to parse it to maintain compatibility. If
206 		 * neither property is present we fall back to the one step
207 		 * per period behavior.
208 		 */
209 		steps_per_period = device_property_read_bool(dev,
210 					"rotary-encoder,half-period") ? 2 : 1;
211 	}
212 
213 	encoder->rollover =
214 		device_property_read_bool(dev, "rotary-encoder,rollover");
215 
216 	device_property_read_u32(dev, "linux,axis", &encoder->axis);
217 	encoder->relative_axis =
218 		device_property_read_bool(dev, "rotary-encoder,relative-axis");
219 
220 	encoder->gpios = devm_gpiod_get_array(dev, NULL, GPIOD_IN);
221 	if (IS_ERR(encoder->gpios)) {
222 		dev_err(dev, "unable to get gpios\n");
223 		return PTR_ERR(encoder->gpios);
224 	}
225 	if (encoder->gpios->ndescs < 2) {
226 		dev_err(dev, "not enough gpios found\n");
227 		return -EINVAL;
228 	}
229 
230 	input = devm_input_allocate_device(dev);
231 	if (!input)
232 		return -ENOMEM;
233 
234 	encoder->input = input;
235 
236 	input->name = pdev->name;
237 	input->id.bustype = BUS_HOST;
238 	input->dev.parent = dev;
239 
240 	if (encoder->relative_axis)
241 		input_set_capability(input, EV_REL, encoder->axis);
242 	else
243 		input_set_abs_params(input,
244 				     encoder->axis, 0, encoder->steps, 0, 1);
245 
246 	switch (steps_per_period >> (encoder->gpios->ndescs - 2)) {
247 	case 4:
248 		handler = &rotary_encoder_quarter_period_irq;
249 		encoder->last_stable = rotary_encoder_get_state(encoder);
250 		break;
251 	case 2:
252 		handler = &rotary_encoder_half_period_irq;
253 		encoder->last_stable = rotary_encoder_get_state(encoder);
254 		break;
255 	case 1:
256 		handler = &rotary_encoder_irq;
257 		break;
258 	default:
259 		dev_err(dev, "'%d' is not a valid steps-per-period value\n",
260 			steps_per_period);
261 		return -EINVAL;
262 	}
263 
264 	encoder->irq =
265 		devm_kzalloc(dev,
266 			     sizeof(*encoder->irq) * encoder->gpios->ndescs,
267 			     GFP_KERNEL);
268 	if (!encoder->irq)
269 		return -ENOMEM;
270 
271 	for (i = 0; i < encoder->gpios->ndescs; ++i) {
272 		encoder->irq[i] = gpiod_to_irq(encoder->gpios->desc[i]);
273 
274 		err = devm_request_threaded_irq(dev, encoder->irq[i],
275 				NULL, handler,
276 				IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING |
277 				IRQF_ONESHOT,
278 				DRV_NAME, encoder);
279 		if (err) {
280 			dev_err(dev, "unable to request IRQ %d (gpio#%d)\n",
281 				encoder->irq[i], i);
282 			return err;
283 		}
284 	}
285 
286 	err = input_register_device(input);
287 	if (err) {
288 		dev_err(dev, "failed to register input device\n");
289 		return err;
290 	}
291 
292 	device_init_wakeup(dev,
293 			   device_property_read_bool(dev, "wakeup-source"));
294 
295 	platform_set_drvdata(pdev, encoder);
296 
297 	return 0;
298 }
299 
300 static int __maybe_unused rotary_encoder_suspend(struct device *dev)
301 {
302 	struct rotary_encoder *encoder = dev_get_drvdata(dev);
303 	unsigned int i;
304 
305 	if (device_may_wakeup(dev)) {
306 		for (i = 0; i < encoder->gpios->ndescs; ++i)
307 			enable_irq_wake(encoder->irq[i]);
308 	}
309 
310 	return 0;
311 }
312 
313 static int __maybe_unused rotary_encoder_resume(struct device *dev)
314 {
315 	struct rotary_encoder *encoder = dev_get_drvdata(dev);
316 	unsigned int i;
317 
318 	if (device_may_wakeup(dev)) {
319 		for (i = 0; i < encoder->gpios->ndescs; ++i)
320 			disable_irq_wake(encoder->irq[i]);
321 	}
322 
323 	return 0;
324 }
325 
326 static SIMPLE_DEV_PM_OPS(rotary_encoder_pm_ops,
327 			 rotary_encoder_suspend, rotary_encoder_resume);
328 
329 #ifdef CONFIG_OF
330 static const struct of_device_id rotary_encoder_of_match[] = {
331 	{ .compatible = "rotary-encoder", },
332 	{ },
333 };
334 MODULE_DEVICE_TABLE(of, rotary_encoder_of_match);
335 #endif
336 
337 static struct platform_driver rotary_encoder_driver = {
338 	.probe		= rotary_encoder_probe,
339 	.driver		= {
340 		.name	= DRV_NAME,
341 		.pm	= &rotary_encoder_pm_ops,
342 		.of_match_table = of_match_ptr(rotary_encoder_of_match),
343 	}
344 };
345 module_platform_driver(rotary_encoder_driver);
346 
347 MODULE_ALIAS("platform:" DRV_NAME);
348 MODULE_DESCRIPTION("GPIO rotary encoder driver");
349 MODULE_AUTHOR("Daniel Mack <daniel@caiaq.de>, Johan Hovold");
350 MODULE_LICENSE("GPL v2");
351