xref: /linux/drivers/input/misc/rotary_encoder.c (revision b8d312aa075f33282565467662c4628dae0a2aff) 
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 	mutex_lock(&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 	mutex_unlock(&encoder->access_mutex);
133 
134 	return IRQ_HANDLED;
135 }
136 
137 static irqreturn_t rotary_encoder_half_period_irq(int irq, void *dev_id)
138 {
139 	struct rotary_encoder *encoder = dev_id;
140 	unsigned int state;
141 
142 	mutex_lock(&encoder->access_mutex);
143 
144 	state = rotary_encoder_get_state(encoder);
145 
146 	if (state & 1) {
147 		encoder->dir = ((encoder->last_stable - state + 1) % 4) - 1;
148 	} else {
149 		if (state != encoder->last_stable) {
150 			rotary_encoder_report_event(encoder);
151 			encoder->last_stable = state;
152 		}
153 	}
154 
155 	mutex_unlock(&encoder->access_mutex);
156 
157 	return IRQ_HANDLED;
158 }
159 
160 static irqreturn_t rotary_encoder_quarter_period_irq(int irq, void *dev_id)
161 {
162 	struct rotary_encoder *encoder = dev_id;
163 	unsigned int state;
164 
165 	mutex_lock(&encoder->access_mutex);
166 
167 	state = rotary_encoder_get_state(encoder);
168 
169 	if ((encoder->last_stable + 1) % 4 == state)
170 		encoder->dir = 1;
171 	else if (encoder->last_stable == (state + 1) % 4)
172 		encoder->dir = -1;
173 	else
174 		goto out;
175 
176 	rotary_encoder_report_event(encoder);
177 
178 out:
179 	encoder->last_stable = state;
180 	mutex_unlock(&encoder->access_mutex);
181 
182 	return IRQ_HANDLED;
183 }
184 
185 static int rotary_encoder_probe(struct platform_device *pdev)
186 {
187 	struct device *dev = &pdev->dev;
188 	struct rotary_encoder *encoder;
189 	struct input_dev *input;
190 	irq_handler_t handler;
191 	u32 steps_per_period;
192 	unsigned int i;
193 	int err;
194 
195 	encoder = devm_kzalloc(dev, sizeof(struct rotary_encoder), GFP_KERNEL);
196 	if (!encoder)
197 		return -ENOMEM;
198 
199 	mutex_init(&encoder->access_mutex);
200 
201 	device_property_read_u32(dev, "rotary-encoder,steps", &encoder->steps);
202 
203 	err = device_property_read_u32(dev, "rotary-encoder,steps-per-period",
204 				       &steps_per_period);
205 	if (err) {
206 		/*
207 		 * The 'half-period' property has been deprecated, you must
208 		 * use 'steps-per-period' and set an appropriate value, but
209 		 * we still need to parse it to maintain compatibility. If
210 		 * neither property is present we fall back to the one step
211 		 * per period behavior.
212 		 */
213 		steps_per_period = device_property_read_bool(dev,
214 					"rotary-encoder,half-period") ? 2 : 1;
215 	}
216 
217 	encoder->rollover =
218 		device_property_read_bool(dev, "rotary-encoder,rollover");
219 
220 	if (!device_property_present(dev, "rotary-encoder,encoding") ||
221 	    !device_property_match_string(dev, "rotary-encoder,encoding",
222 					  "gray")) {
223 		dev_info(dev, "gray");
224 		encoder->encoding = ROTENC_GRAY;
225 	} else if (!device_property_match_string(dev, "rotary-encoder,encoding",
226 						 "binary")) {
227 		dev_info(dev, "binary");
228 		encoder->encoding = ROTENC_BINARY;
229 	} else {
230 		dev_err(dev, "unknown encoding setting\n");
231 		return -EINVAL;
232 	}
233 
234 	device_property_read_u32(dev, "linux,axis", &encoder->axis);
235 	encoder->relative_axis =
236 		device_property_read_bool(dev, "rotary-encoder,relative-axis");
237 
238 	encoder->gpios = devm_gpiod_get_array(dev, NULL, GPIOD_IN);
239 	if (IS_ERR(encoder->gpios)) {
240 		err = PTR_ERR(encoder->gpios);
241 		if (err != -EPROBE_DEFER)
242 			dev_err(dev, "unable to get gpios: %d\n", err);
243 		return err;
244 	}
245 	if (encoder->gpios->ndescs < 2) {
246 		dev_err(dev, "not enough gpios found\n");
247 		return -EINVAL;
248 	}
249 
250 	input = devm_input_allocate_device(dev);
251 	if (!input)
252 		return -ENOMEM;
253 
254 	encoder->input = input;
255 
256 	input->name = pdev->name;
257 	input->id.bustype = BUS_HOST;
258 	input->dev.parent = dev;
259 
260 	if (encoder->relative_axis)
261 		input_set_capability(input, EV_REL, encoder->axis);
262 	else
263 		input_set_abs_params(input,
264 				     encoder->axis, 0, encoder->steps, 0, 1);
265 
266 	switch (steps_per_period >> (encoder->gpios->ndescs - 2)) {
267 	case 4:
268 		handler = &rotary_encoder_quarter_period_irq;
269 		encoder->last_stable = rotary_encoder_get_state(encoder);
270 		break;
271 	case 2:
272 		handler = &rotary_encoder_half_period_irq;
273 		encoder->last_stable = rotary_encoder_get_state(encoder);
274 		break;
275 	case 1:
276 		handler = &rotary_encoder_irq;
277 		break;
278 	default:
279 		dev_err(dev, "'%d' is not a valid steps-per-period value\n",
280 			steps_per_period);
281 		return -EINVAL;
282 	}
283 
284 	encoder->irq =
285 		devm_kcalloc(dev,
286 			     encoder->gpios->ndescs, sizeof(*encoder->irq),
287 			     GFP_KERNEL);
288 	if (!encoder->irq)
289 		return -ENOMEM;
290 
291 	for (i = 0; i < encoder->gpios->ndescs; ++i) {
292 		encoder->irq[i] = gpiod_to_irq(encoder->gpios->desc[i]);
293 
294 		err = devm_request_threaded_irq(dev, encoder->irq[i],
295 				NULL, handler,
296 				IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING |
297 				IRQF_ONESHOT,
298 				DRV_NAME, encoder);
299 		if (err) {
300 			dev_err(dev, "unable to request IRQ %d (gpio#%d)\n",
301 				encoder->irq[i], i);
302 			return err;
303 		}
304 	}
305 
306 	err = input_register_device(input);
307 	if (err) {
308 		dev_err(dev, "failed to register input device\n");
309 		return err;
310 	}
311 
312 	device_init_wakeup(dev,
313 			   device_property_read_bool(dev, "wakeup-source"));
314 
315 	platform_set_drvdata(pdev, encoder);
316 
317 	return 0;
318 }
319 
320 static int __maybe_unused rotary_encoder_suspend(struct device *dev)
321 {
322 	struct rotary_encoder *encoder = dev_get_drvdata(dev);
323 	unsigned int i;
324 
325 	if (device_may_wakeup(dev)) {
326 		for (i = 0; i < encoder->gpios->ndescs; ++i)
327 			enable_irq_wake(encoder->irq[i]);
328 	}
329 
330 	return 0;
331 }
332 
333 static int __maybe_unused rotary_encoder_resume(struct device *dev)
334 {
335 	struct rotary_encoder *encoder = dev_get_drvdata(dev);
336 	unsigned int i;
337 
338 	if (device_may_wakeup(dev)) {
339 		for (i = 0; i < encoder->gpios->ndescs; ++i)
340 			disable_irq_wake(encoder->irq[i]);
341 	}
342 
343 	return 0;
344 }
345 
346 static SIMPLE_DEV_PM_OPS(rotary_encoder_pm_ops,
347 			 rotary_encoder_suspend, rotary_encoder_resume);
348 
349 #ifdef CONFIG_OF
350 static const struct of_device_id rotary_encoder_of_match[] = {
351 	{ .compatible = "rotary-encoder", },
352 	{ },
353 };
354 MODULE_DEVICE_TABLE(of, rotary_encoder_of_match);
355 #endif
356 
357 static struct platform_driver rotary_encoder_driver = {
358 	.probe		= rotary_encoder_probe,
359 	.driver		= {
360 		.name	= DRV_NAME,
361 		.pm	= &rotary_encoder_pm_ops,
362 		.of_match_table = of_match_ptr(rotary_encoder_of_match),
363 	}
364 };
365 module_platform_driver(rotary_encoder_driver);
366 
367 MODULE_ALIAS("platform:" DRV_NAME);
368 MODULE_DESCRIPTION("GPIO rotary encoder driver");
369 MODULE_AUTHOR("Daniel Mack <daniel@caiaq.de>, Johan Hovold");
370 MODULE_LICENSE("GPL v2");
371