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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 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 last_stable;
 51 };
 52 
 53 static unsigned rotary_encoder_get_state(struct rotary_encoder *encoder)
 54 {
 55         int i;
 56         unsigned 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 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 

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