xref: /linux/drivers/input/misc/rotary_encoder.c (revision 7f4f3b14e8079ecde096bd734af10e30d40c27b7) 
1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * rotary_encoder.c
4  *
5  * (c) 2009 Daniel Mack <daniel@caiaq.de>
6  * Copyright (C) 2011 Johan Hovold <jhovold@gmail.com>
7  *
8  * state machine code inspired by code from Tim Ruetz
9  *
10  * A generic driver for rotary encoders connected to GPIO lines.
11  * See file:Documentation/input/devices/rotary-encoder.rst for more information
12  */
13 
14 #include <linux/kernel.h>
15 #include <linux/module.h>
16 #include <linux/interrupt.h>
17 #include <linux/input.h>
18 #include <linux/device.h>
19 #include <linux/platform_device.h>
20 #include <linux/gpio/consumer.h>
21 #include <linux/slab.h>
22 #include <linux/of.h>
23 #include <linux/pm.h>
24 #include <linux/property.h>
25 
26 #define DRV_NAME "rotary-encoder"
27 
28 enum rotary_encoder_encoding {
29 	ROTENC_GRAY,
30 	ROTENC_BINARY,
31 };
32 
33 struct rotary_encoder {
34 	struct input_dev *input;
35 
36 	struct mutex access_mutex;
37 
38 	u32 steps;
39 	u32 axis;
40 	bool relative_axis;
41 	bool rollover;
42 	enum rotary_encoder_encoding encoding;
43 
44 	unsigned int pos;
45 
46 	struct gpio_descs *gpios;
47 
48 	unsigned int *irq;
49 
50 	bool armed;
51 	signed char dir;	/* 1 - clockwise, -1 - CCW */
52 
53 	unsigned int last_stable;
54 };
55 
56 static unsigned int rotary_encoder_get_state(struct rotary_encoder *encoder)
57 {
58 	int i;
59 	unsigned int ret = 0;
60 
61 	for (i = 0; i < encoder->gpios->ndescs; ++i) {
62 		int val = gpiod_get_value_cansleep(encoder->gpios->desc[i]);
63 
64 		/* convert from gray encoding to normal */
65 		if (encoder->encoding == ROTENC_GRAY && ret & 1)
66 			val = !val;
67 
68 		ret = ret << 1 | val;
69 	}
70 
71 	return ret & 3;
72 }
73 
74 static void rotary_encoder_report_event(struct rotary_encoder *encoder)
75 {
76 	if (encoder->relative_axis) {
77 		input_report_rel(encoder->input,
78 				 encoder->axis, encoder->dir);
79 	} else {
80 		unsigned int pos = encoder->pos;
81 
82 		if (encoder->dir < 0) {
83 			/* turning counter-clockwise */
84 			if (encoder->rollover)
85 				pos += encoder->steps;
86 			if (pos)
87 				pos--;
88 		} else {
89 			/* turning clockwise */
90 			if (encoder->rollover || pos < encoder->steps)
91 				pos++;
92 		}
93 
94 		if (encoder->rollover)
95 			pos %= encoder->steps;
96 
97 		encoder->pos = pos;
98 		input_report_abs(encoder->input, encoder->axis, encoder->pos);
99 	}
100 
101 	input_sync(encoder->input);
102 }
103 
104 static irqreturn_t rotary_encoder_irq(int irq, void *dev_id)
105 {
106 	struct rotary_encoder *encoder = dev_id;
107 	unsigned int state;
108 
109 	guard(mutex)(&encoder->access_mutex);
110 
111 	state = rotary_encoder_get_state(encoder);
112 
113 	switch (state) {
114 	case 0x0:
115 		if (encoder->armed) {
116 			rotary_encoder_report_event(encoder);
117 			encoder->armed = false;
118 		}
119 		break;
120 
121 	case 0x1:
122 	case 0x3:
123 		if (encoder->armed)
124 			encoder->dir = 2 - state;
125 		break;
126 
127 	case 0x2:
128 		encoder->armed = true;
129 		break;
130 	}
131 
132 	return IRQ_HANDLED;
133 }
134 
135 static irqreturn_t rotary_encoder_half_period_irq(int irq, void *dev_id)
136 {
137 	struct rotary_encoder *encoder = dev_id;
138 	unsigned int state;
139 
140 	guard(mutex)(&encoder->access_mutex);
141 
142 	state = rotary_encoder_get_state(encoder);
143 
144 	if (state & 1) {
145 		encoder->dir = ((encoder->last_stable - state + 1) % 4) - 1;
146 	} else {
147 		if (state != encoder->last_stable) {
148 			rotary_encoder_report_event(encoder);
149 			encoder->last_stable = state;
150 		}
151 	}
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 	guard(mutex)(&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 		rotary_encoder_report_event(encoder);
168 	} else if (encoder->last_stable == (state + 1) % 4) {
169 		encoder->dir = -1;
170 		rotary_encoder_report_event(encoder);
171 	}
172 
173 	encoder->last_stable = state;
174 
175 	return IRQ_HANDLED;
176 }
177 
178 static int rotary_encoder_probe(struct platform_device *pdev)
179 {
180 	struct device *dev = &pdev->dev;
181 	struct rotary_encoder *encoder;
182 	struct input_dev *input;
183 	irq_handler_t handler;
184 	u32 steps_per_period;
185 	unsigned int i;
186 	int err;
187 
188 	encoder = devm_kzalloc(dev, sizeof(struct rotary_encoder), GFP_KERNEL);
189 	if (!encoder)
190 		return -ENOMEM;
191 
192 	mutex_init(&encoder->access_mutex);
193 
194 	device_property_read_u32(dev, "rotary-encoder,steps", &encoder->steps);
195 
196 	err = device_property_read_u32(dev, "rotary-encoder,steps-per-period",
197 				       &steps_per_period);
198 	if (err) {
199 		/*
200 		 * The 'half-period' property has been deprecated, you must
201 		 * use 'steps-per-period' and set an appropriate value, but
202 		 * we still need to parse it to maintain compatibility. If
203 		 * neither property is present we fall back to the one step
204 		 * per period behavior.
205 		 */
206 		steps_per_period = device_property_read_bool(dev,
207 					"rotary-encoder,half-period") ? 2 : 1;
208 	}
209 
210 	encoder->rollover =
211 		device_property_read_bool(dev, "rotary-encoder,rollover");
212 
213 	if (!device_property_present(dev, "rotary-encoder,encoding") ||
214 	    !device_property_match_string(dev, "rotary-encoder,encoding",
215 					  "gray")) {
216 		dev_info(dev, "gray");
217 		encoder->encoding = ROTENC_GRAY;
218 	} else if (!device_property_match_string(dev, "rotary-encoder,encoding",
219 						 "binary")) {
220 		dev_info(dev, "binary");
221 		encoder->encoding = ROTENC_BINARY;
222 	} else {
223 		dev_err(dev, "unknown encoding setting\n");
224 		return -EINVAL;
225 	}
226 
227 	device_property_read_u32(dev, "linux,axis", &encoder->axis);
228 	encoder->relative_axis =
229 		device_property_read_bool(dev, "rotary-encoder,relative-axis");
230 
231 	encoder->gpios = devm_gpiod_get_array(dev, NULL, GPIOD_IN);
232 	if (IS_ERR(encoder->gpios))
233 		return dev_err_probe(dev, PTR_ERR(encoder->gpios), "unable to get gpios\n");
234 	if (encoder->gpios->ndescs < 2) {
235 		dev_err(dev, "not enough gpios found\n");
236 		return -EINVAL;
237 	}
238 
239 	input = devm_input_allocate_device(dev);
240 	if (!input)
241 		return -ENOMEM;
242 
243 	encoder->input = input;
244 
245 	input->name = pdev->name;
246 	input->id.bustype = BUS_HOST;
247 
248 	if (encoder->relative_axis)
249 		input_set_capability(input, EV_REL, encoder->axis);
250 	else
251 		input_set_abs_params(input,
252 				     encoder->axis, 0, encoder->steps, 0, 1);
253 
254 	switch (steps_per_period >> (encoder->gpios->ndescs - 2)) {
255 	case 4:
256 		handler = &rotary_encoder_quarter_period_irq;
257 		encoder->last_stable = rotary_encoder_get_state(encoder);
258 		break;
259 	case 2:
260 		handler = &rotary_encoder_half_period_irq;
261 		encoder->last_stable = rotary_encoder_get_state(encoder);
262 		break;
263 	case 1:
264 		handler = &rotary_encoder_irq;
265 		break;
266 	default:
267 		dev_err(dev, "'%d' is not a valid steps-per-period value\n",
268 			steps_per_period);
269 		return -EINVAL;
270 	}
271 
272 	encoder->irq =
273 		devm_kcalloc(dev,
274 			     encoder->gpios->ndescs, sizeof(*encoder->irq),
275 			     GFP_KERNEL);
276 	if (!encoder->irq)
277 		return -ENOMEM;
278 
279 	for (i = 0; i < encoder->gpios->ndescs; ++i) {
280 		encoder->irq[i] = gpiod_to_irq(encoder->gpios->desc[i]);
281 
282 		err = devm_request_threaded_irq(dev, encoder->irq[i],
283 				NULL, handler,
284 				IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING |
285 				IRQF_ONESHOT,
286 				DRV_NAME, encoder);
287 		if (err) {
288 			dev_err(dev, "unable to request IRQ %d (gpio#%d)\n",
289 				encoder->irq[i], i);
290 			return err;
291 		}
292 	}
293 
294 	err = input_register_device(input);
295 	if (err) {
296 		dev_err(dev, "failed to register input device\n");
297 		return err;
298 	}
299 
300 	device_init_wakeup(dev,
301 			   device_property_read_bool(dev, "wakeup-source"));
302 
303 	platform_set_drvdata(pdev, encoder);
304 
305 	return 0;
306 }
307 
308 static int rotary_encoder_suspend(struct device *dev)
309 {
310 	struct rotary_encoder *encoder = dev_get_drvdata(dev);
311 	unsigned int i;
312 
313 	if (device_may_wakeup(dev)) {
314 		for (i = 0; i < encoder->gpios->ndescs; ++i)
315 			enable_irq_wake(encoder->irq[i]);
316 	}
317 
318 	return 0;
319 }
320 
321 static int rotary_encoder_resume(struct device *dev)
322 {
323 	struct rotary_encoder *encoder = dev_get_drvdata(dev);
324 	unsigned int i;
325 
326 	if (device_may_wakeup(dev)) {
327 		for (i = 0; i < encoder->gpios->ndescs; ++i)
328 			disable_irq_wake(encoder->irq[i]);
329 	}
330 
331 	return 0;
332 }
333 
334 static DEFINE_SIMPLE_DEV_PM_OPS(rotary_encoder_pm_ops,
335 				rotary_encoder_suspend, rotary_encoder_resume);
336 
337 #ifdef CONFIG_OF
338 static const struct of_device_id rotary_encoder_of_match[] = {
339 	{ .compatible = "rotary-encoder", },
340 	{ },
341 };
342 MODULE_DEVICE_TABLE(of, rotary_encoder_of_match);
343 #endif
344 
345 static struct platform_driver rotary_encoder_driver = {
346 	.probe		= rotary_encoder_probe,
347 	.driver		= {
348 		.name	= DRV_NAME,
349 		.pm	= pm_sleep_ptr(&rotary_encoder_pm_ops),
350 		.of_match_table = of_match_ptr(rotary_encoder_of_match),
351 	}
352 };
353 module_platform_driver(rotary_encoder_driver);
354 
355 MODULE_ALIAS("platform:" DRV_NAME);
356 MODULE_DESCRIPTION("GPIO rotary encoder driver");
357 MODULE_AUTHOR("Daniel Mack <daniel@caiaq.de>, Johan Hovold");
358 MODULE_LICENSE("GPL v2");
359