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Linux/drivers/input/misc/rotary_encoder.c

  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 enum rotary_encoder_encoding {
 32         ROTENC_GRAY,
 33         ROTENC_BINARY,
 34 };
 35 
 36 struct rotary_encoder {
 37         struct input_dev *input;
 38 
 39         struct mutex access_mutex;
 40 
 41         u32 steps;
 42         u32 axis;
 43         bool relative_axis;
 44         bool rollover;
 45         enum rotary_encoder_encoding encoding;
 46 
 47         unsigned int pos;
 48 
 49         struct gpio_descs *gpios;
 50 
 51         unsigned int *irq;
 52 
 53         bool armed;
 54         signed char dir;        /* 1 - clockwise, -1 - CCW */
 55 
 56         unsigned int last_stable;
 57 };
 58 
 59 static unsigned int rotary_encoder_get_state(struct rotary_encoder *encoder)
 60 {
 61         int i;
 62         unsigned int ret = 0;
 63 
 64         for (i = 0; i < encoder->gpios->ndescs; ++i) {
 65                 int val = gpiod_get_value_cansleep(encoder->gpios->desc[i]);
 66 
 67                 /* convert from gray encoding to normal */
 68                 if (encoder->encoding == ROTENC_GRAY && ret & 1)
 69                         val = !val;
 70 
 71                 ret = ret << 1 | val;
 72         }
 73 
 74         return ret & 3;
 75 }
 76 
 77 static void rotary_encoder_report_event(struct rotary_encoder *encoder)
 78 {
 79         if (encoder->relative_axis) {
 80                 input_report_rel(encoder->input,
 81                                  encoder->axis, encoder->dir);
 82         } else {
 83                 unsigned int pos = encoder->pos;
 84 
 85                 if (encoder->dir < 0) {
 86                         /* turning counter-clockwise */
 87                         if (encoder->rollover)
 88                                 pos += encoder->steps;
 89                         if (pos)
 90                                 pos--;
 91                 } else {
 92                         /* turning clockwise */
 93                         if (encoder->rollover || pos < encoder->steps)
 94                                 pos++;
 95                 }
 96 
 97                 if (encoder->rollover)
 98                         pos %= encoder->steps;
 99 
100                 encoder->pos = pos;
101                 input_report_abs(encoder->input, encoder->axis, encoder->pos);
102         }
103 
104         input_sync(encoder->input);
105 }
106 
107 static irqreturn_t rotary_encoder_irq(int irq, void *dev_id)
108 {
109         struct rotary_encoder *encoder = dev_id;
110         unsigned int state;
111 
112         mutex_lock(&encoder->access_mutex);
113 
114         state = rotary_encoder_get_state(encoder);
115 
116         switch (state) {
117         case 0x0:
118                 if (encoder->armed) {
119                         rotary_encoder_report_event(encoder);
120                         encoder->armed = false;
121                 }
122                 break;
123 
124         case 0x1:
125         case 0x3:
126                 if (encoder->armed)
127                         encoder->dir = 2 - state;
128                 break;
129 
130         case 0x2:
131                 encoder->armed = true;
132                 break;
133         }
134 
135         mutex_unlock(&encoder->access_mutex);
136 
137         return IRQ_HANDLED;
138 }
139 
140 static irqreturn_t rotary_encoder_half_period_irq(int irq, void *dev_id)
141 {
142         struct rotary_encoder *encoder = dev_id;
143         unsigned int state;
144 
145         mutex_lock(&encoder->access_mutex);
146 
147         state = rotary_encoder_get_state(encoder);
148 
149         if (state & 1) {
150                 encoder->dir = ((encoder->last_stable - state + 1) % 4) - 1;
151         } else {
152                 if (state != encoder->last_stable) {
153                         rotary_encoder_report_event(encoder);
154                         encoder->last_stable = state;
155                 }
156         }
157 
158         mutex_unlock(&encoder->access_mutex);
159 
160         return IRQ_HANDLED;
161 }
162 
163 static irqreturn_t rotary_encoder_quarter_period_irq(int irq, void *dev_id)
164 {
165         struct rotary_encoder *encoder = dev_id;
166         unsigned int state;
167 
168         mutex_lock(&encoder->access_mutex);
169 
170         state = rotary_encoder_get_state(encoder);
171 
172         if ((encoder->last_stable + 1) % 4 == state)
173                 encoder->dir = 1;
174         else if (encoder->last_stable == (state + 1) % 4)
175                 encoder->dir = -1;
176         else
177                 goto out;
178 
179         rotary_encoder_report_event(encoder);
180 
181 out:
182         encoder->last_stable = state;
183         mutex_unlock(&encoder->access_mutex);
184 
185         return IRQ_HANDLED;
186 }
187 
188 static int rotary_encoder_probe(struct platform_device *pdev)
189 {
190         struct device *dev = &pdev->dev;
191         struct rotary_encoder *encoder;
192         struct input_dev *input;
193         irq_handler_t handler;
194         u32 steps_per_period;
195         unsigned int i;
196         int err;
197 
198         encoder = devm_kzalloc(dev, sizeof(struct rotary_encoder), GFP_KERNEL);
199         if (!encoder)
200                 return -ENOMEM;
201 
202         mutex_init(&encoder->access_mutex);
203 
204         device_property_read_u32(dev, "rotary-encoder,steps", &encoder->steps);
205 
206         err = device_property_read_u32(dev, "rotary-encoder,steps-per-period",
207                                        &steps_per_period);
208         if (err) {
209                 /*
210                  * The 'half-period' property has been deprecated, you must
211                  * use 'steps-per-period' and set an appropriate value, but
212                  * we still need to parse it to maintain compatibility. If
213                  * neither property is present we fall back to the one step
214                  * per period behavior.
215                  */
216                 steps_per_period = device_property_read_bool(dev,
217                                         "rotary-encoder,half-period") ? 2 : 1;
218         }
219 
220         encoder->rollover =
221                 device_property_read_bool(dev, "rotary-encoder,rollover");
222 
223         if (!device_property_present(dev, "rotary-encoder,encoding") ||
224             !device_property_match_string(dev, "rotary-encoder,encoding",
225                                           "gray")) {
226                 dev_info(dev, "gray");
227                 encoder->encoding = ROTENC_GRAY;
228         } else if (!device_property_match_string(dev, "rotary-encoder,encoding",
229                                                  "binary")) {
230                 dev_info(dev, "binary");
231                 encoder->encoding = ROTENC_BINARY;
232         } else {
233                 dev_err(dev, "unknown encoding setting\n");
234                 return -EINVAL;
235         }
236 
237         device_property_read_u32(dev, "linux,axis", &encoder->axis);
238         encoder->relative_axis =
239                 device_property_read_bool(dev, "rotary-encoder,relative-axis");
240 
241         encoder->gpios = devm_gpiod_get_array(dev, NULL, GPIOD_IN);
242         if (IS_ERR(encoder->gpios)) {
243                 dev_err(dev, "unable to get gpios\n");
244                 return PTR_ERR(encoder->gpios);
245         }
246         if (encoder->gpios->ndescs < 2) {
247                 dev_err(dev, "not enough gpios found\n");
248                 return -EINVAL;
249         }
250 
251         input = devm_input_allocate_device(dev);
252         if (!input)
253                 return -ENOMEM;
254 
255         encoder->input = input;
256 
257         input->name = pdev->name;
258         input->id.bustype = BUS_HOST;
259         input->dev.parent = dev;
260 
261         if (encoder->relative_axis)
262                 input_set_capability(input, EV_REL, encoder->axis);
263         else
264                 input_set_abs_params(input,
265                                      encoder->axis, 0, encoder->steps, 0, 1);
266 
267         switch (steps_per_period >> (encoder->gpios->ndescs - 2)) {
268         case 4:
269                 handler = &rotary_encoder_quarter_period_irq;
270                 encoder->last_stable = rotary_encoder_get_state(encoder);
271                 break;
272         case 2:
273                 handler = &rotary_encoder_half_period_irq;
274                 encoder->last_stable = rotary_encoder_get_state(encoder);
275                 break;
276         case 1:
277                 handler = &rotary_encoder_irq;
278                 break;
279         default:
280                 dev_err(dev, "'%d' is not a valid steps-per-period value\n",
281                         steps_per_period);
282                 return -EINVAL;
283         }
284 
285         encoder->irq =
286                 devm_kzalloc(dev,
287                              sizeof(*encoder->irq) * encoder->gpios->ndescs,
288                              GFP_KERNEL);
289         if (!encoder->irq)
290                 return -ENOMEM;
291 
292         for (i = 0; i < encoder->gpios->ndescs; ++i) {
293                 encoder->irq[i] = gpiod_to_irq(encoder->gpios->desc[i]);
294 
295                 err = devm_request_threaded_irq(dev, encoder->irq[i],
296                                 NULL, handler,
297                                 IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING |
298                                 IRQF_ONESHOT,
299                                 DRV_NAME, encoder);
300                 if (err) {
301                         dev_err(dev, "unable to request IRQ %d (gpio#%d)\n",
302                                 encoder->irq[i], i);
303                         return err;
304                 }
305         }
306 
307         err = input_register_device(input);
308         if (err) {
309                 dev_err(dev, "failed to register input device\n");
310                 return err;
311         }
312 
313         device_init_wakeup(dev,
314                            device_property_read_bool(dev, "wakeup-source"));
315 
316         platform_set_drvdata(pdev, encoder);
317 
318         return 0;
319 }
320 
321 static int __maybe_unused rotary_encoder_suspend(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                         enable_irq_wake(encoder->irq[i]);
329         }
330 
331         return 0;
332 }
333 
334 static int __maybe_unused rotary_encoder_resume(struct device *dev)
335 {
336         struct rotary_encoder *encoder = dev_get_drvdata(dev);
337         unsigned int i;
338 
339         if (device_may_wakeup(dev)) {
340                 for (i = 0; i < encoder->gpios->ndescs; ++i)
341                         disable_irq_wake(encoder->irq[i]);
342         }
343 
344         return 0;
345 }
346 
347 static SIMPLE_DEV_PM_OPS(rotary_encoder_pm_ops,
348                          rotary_encoder_suspend, rotary_encoder_resume);
349 
350 #ifdef CONFIG_OF
351 static const struct of_device_id rotary_encoder_of_match[] = {
352         { .compatible = "rotary-encoder", },
353         { },
354 };
355 MODULE_DEVICE_TABLE(of, rotary_encoder_of_match);
356 #endif
357 
358 static struct platform_driver rotary_encoder_driver = {
359         .probe          = rotary_encoder_probe,
360         .driver         = {
361                 .name   = DRV_NAME,
362                 .pm     = &rotary_encoder_pm_ops,
363                 .of_match_table = of_match_ptr(rotary_encoder_of_match),
364         }
365 };
366 module_platform_driver(rotary_encoder_driver);
367 
368 MODULE_ALIAS("platform:" DRV_NAME);
369 MODULE_DESCRIPTION("GPIO rotary encoder driver");
370 MODULE_AUTHOR("Daniel Mack <daniel@caiaq.de>, Johan Hovold");
371 MODULE_LICENSE("GPL v2");
372 

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