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
28enum rotary_encoder_encoding {
29 ROTENC_GRAY,
30 ROTENC_BINARY,
31};
32
33struct 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
56static 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(desc: 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
74static void rotary_encoder_report_event(struct rotary_encoder *encoder)
75{
76 if (encoder->relative_axis) {
77 input_report_rel(dev: encoder->input,
78 code: encoder->axis, value: 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(dev: encoder->input, code: encoder->axis, value: encoder->pos);
99 }
100
101 input_sync(dev: encoder->input);
102}
103
104static 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)(T: &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
135static 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)(T: &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
156static 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)(T: &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
178static 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, size: 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, propname: "rotary-encoder,steps", val: &encoder->steps);
195
196 err = device_property_read_u32(dev, propname: "rotary-encoder,steps-per-period",
197 val: &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 propname: "rotary-encoder,half-period") ? 2 : 1;
208 }
209
210 encoder->rollover =
211 device_property_read_bool(dev, propname: "rotary-encoder,rollover");
212
213 if (!device_property_present(dev, propname: "rotary-encoder,encoding") ||
214 !device_property_match_string(dev, propname: "rotary-encoder,encoding",
215 string: "gray")) {
216 dev_info(dev, "gray");
217 encoder->encoding = ROTENC_GRAY;
218 } else if (!device_property_match_string(dev, propname: "rotary-encoder,encoding",
219 string: "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, propname: "linux,axis", val: &encoder->axis);
228 encoder->relative_axis =
229 device_property_read_bool(dev, propname: "rotary-encoder,relative-axis");
230
231 encoder->gpios = devm_gpiod_get_array(dev, NULL, flags: GPIOD_IN);
232 if (IS_ERR(ptr: encoder->gpios))
233 return dev_err_probe(dev, err: PTR_ERR(ptr: encoder->gpios), fmt: "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(dev: input, EV_REL, code: encoder->axis);
250 else
251 input_set_abs_params(dev: input,
252 axis: encoder->axis, min: 0, max: encoder->steps, fuzz: 0, flat: 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 n: encoder->gpios->ndescs, size: 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(desc: encoder->gpios->desc[i]);
281
282 err = devm_request_threaded_irq(dev, irq: encoder->irq[i],
283 NULL, thread_fn: handler,
284 IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING |
285 IRQF_ONESHOT,
286 DRV_NAME, dev_id: 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 enable: device_property_read_bool(dev, propname: "wakeup-source"));
302
303 platform_set_drvdata(pdev, data: encoder);
304
305 return 0;
306}
307
308static 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(irq: encoder->irq[i]);
316 }
317
318 return 0;
319}
320
321static 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(irq: encoder->irq[i]);
329 }
330
331 return 0;
332}
333
334static DEFINE_SIMPLE_DEV_PM_OPS(rotary_encoder_pm_ops,
335 rotary_encoder_suspend, rotary_encoder_resume);
336
337#ifdef CONFIG_OF
338static const struct of_device_id rotary_encoder_of_match[] = {
339 { .compatible = "rotary-encoder", },
340 { },
341};
342MODULE_DEVICE_TABLE(of, rotary_encoder_of_match);
343#endif
344
345static 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};
353module_platform_driver(rotary_encoder_driver);
354
355MODULE_ALIAS("platform:" DRV_NAME);
356MODULE_DESCRIPTION("GPIO rotary encoder driver");
357MODULE_AUTHOR("Daniel Mack <daniel@caiaq.de>, Johan Hovold");
358MODULE_LICENSE("GPL v2");
359

source code of linux/drivers/input/misc/rotary_encoder.c