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_desc *gpio_a;
  44         struct gpio_desc *gpio_b;
  45
  46         unsigned int irq_a;
  47         unsigned int irq_b;
  48
  49         bool armed;
  50         unsigned char dir;      /* 0 - clockwise, 1 - CCW */
  51
  52         char last_stable;
  53 };
  54
  55 static int rotary_encoder_get_state(struct rotary_encoder *encoder)
  56 {
  57         int a = !!gpiod_get_value_cansleep(encoder->gpio_a);
  58         int b = !!gpiod_get_value_cansleep(encoder->gpio_b);
  59
  60         return ((a << 1) | b);
  61 }
  62
  63 static void rotary_encoder_report_event(struct rotary_encoder *encoder)
  64 {
  65         if (encoder->relative_axis) {
  66                 input_report_rel(encoder->input,
  67                                  encoder->axis, encoder->dir ? -1 : 1);
  68         } else {
  69                 unsigned int pos = encoder->pos;
  70
  71                 if (encoder->dir) {
  72                         /* turning counter-clockwise */
  73                         if (encoder->rollover)
  74                                 pos += encoder->steps;
  75                         if (pos)
  76                                 pos--;
  77                 } else {
  78                         /* turning clockwise */
  79                         if (encoder->rollover || pos < encoder->steps)
  80                                 pos++;
  81                 }
  82
  83                 if (encoder->rollover)
  84                         pos %= encoder->steps;
  85
  86                 encoder->pos = pos;
  87                 input_report_abs(encoder->input, encoder->axis, encoder->pos);
  88         }
  89
  90         input_sync(encoder->input);
  91 }
  92
  93 static irqreturn_t rotary_encoder_irq(int irq, void *dev_id)
  94 {
  95         struct rotary_encoder *encoder = dev_id;
  96         int state;
  97
  98         mutex_lock(&encoder->access_mutex);
  99
 100         state = rotary_encoder_get_state(encoder);
 101
 102         switch (state) {
 103         case 0x0:
 104                 if (encoder->armed) {
 105                         rotary_encoder_report_event(encoder);
 106                         encoder->armed = false;
 107                 }
 108                 break;
 109
 110         case 0x1:
 111         case 0x2:
 112                 if (encoder->armed)
 113                         encoder->dir = state - 1;
 114                 break;
 115
 116         case 0x3:
 117                 encoder->armed = true;
 118                 break;
 119         }
 120
 121         mutex_unlock(&encoder->access_mutex);
 122
 123         return IRQ_HANDLED;
 124 }
 125
 126 static irqreturn_t rotary_encoder_half_period_irq(int irq, void *dev_id)
 127 {
 128         struct rotary_encoder *encoder = dev_id;
 129         int state;
 130
 131         mutex_lock(&encoder->access_mutex);
 132
 133         state = rotary_encoder_get_state(encoder);
 134
 135         switch (state) {
 136         case 0x00:
 137         case 0x03:
 138                 if (state != encoder->last_stable) {
 139                         rotary_encoder_report_event(encoder);
 140                         encoder->last_stable = state;
 141                 }
 142                 break;
 143
 144         case 0x01:
 145         case 0x02:
 146                 encoder->dir = (encoder->last_stable + state) & 0x01;
 147                 break;
 148         }
 149
 150         mutex_unlock(&encoder->access_mutex);
 151
 152         return IRQ_HANDLED;
 153 }
 154
 155 static irqreturn_t rotary_encoder_quarter_period_irq(int irq, void *dev_id)
 156 {
 157         struct rotary_encoder *encoder = dev_id;
 158         unsigned char sum;
 159         int state;
 160
 161         mutex_lock(&encoder->access_mutex);
 162
 163         state = rotary_encoder_get_state(encoder);
 164
 165         /*
 166          * We encode the previous and the current state using a byte.
 167          * The previous state in the MSB nibble, the current state in the LSB
 168          * nibble. Then use a table to decide the direction of the turn.
 169          */
 170         sum = (encoder->last_stable << 4) + state;
 171         switch (sum) {
 172         case 0x31:
 173         case 0x10:
 174         case 0x02:
 175         case 0x23:
 176                 encoder->dir = 0; /* clockwise */
 177                 break;
 178
 179         case 0x13:
 180         case 0x01:
 181         case 0x20:
 182         case 0x32:
 183                 encoder->dir = 1; /* counter-clockwise */
 184                 break;
 185
 186         default:
 187                 /*
 188                  * Ignore all other values. This covers the case when the
 189                  * state didn't change (a spurious interrupt) and the
 190                  * cases where the state changed by two steps, making it
 191                  * impossible to tell the direction.
 192                  *
 193                  * In either case, don't report any event and save the
 194                  * state for later.
 195                  */
 196                 goto out;
 197         }
 198
 199         rotary_encoder_report_event(encoder);
 200
 201 out:
 202         encoder->last_stable = state;
 203         mutex_unlock(&encoder->access_mutex);
 204
 205         return IRQ_HANDLED;
 206 }
 207
 208 static int rotary_encoder_probe(struct platform_device *pdev)
 209 {
 210         struct device *dev = &pdev->dev;
 211         struct rotary_encoder *encoder;
 212         struct input_dev *input;
 213         irq_handler_t handler;
 214         u32 steps_per_period;
 215         int err;
 216
 217         encoder = devm_kzalloc(dev, sizeof(struct rotary_encoder), GFP_KERNEL);
 218         if (!encoder)
 219                 return -ENOMEM;
 220
 221         mutex_init(&encoder->access_mutex);
 222
 223         device_property_read_u32(dev, "rotary-encoder,steps", &encoder->steps);
 224
 225         err = device_property_read_u32(dev, "rotary-encoder,steps-per-period",
 226                                        &steps_per_period);
 227         if (err) {
 228                 /*
 229                  * The 'half-period' property has been deprecated, you must
 230                  * use 'steps-per-period' and set an appropriate value, but
 231                  * we still need to parse it to maintain compatibility. If
 232                  * neither property is present we fall back to the one step
 233                  * per period behavior.
 234                  */
 235                 steps_per_period = device_property_read_bool(dev,
 236                                         "rotary-encoder,half-period") ? 2 : 1;
 237         }
 238
 239         encoder->rollover =
 240                 device_property_read_bool(dev, "rotary-encoder,rollover");
 241
 242         device_property_read_u32(dev, "linux,axis", &encoder->axis);
 243         encoder->relative_axis =
 244                 device_property_read_bool(dev, "rotary-encoder,relative-axis");
 245
 246         encoder->gpio_a = devm_gpiod_get_index(dev, NULL, 0, GPIOD_IN);
 247         if (IS_ERR(encoder->gpio_a)) {
 248                 err = PTR_ERR(encoder->gpio_a);
 249                 dev_err(dev, "unable to get GPIO at index 0: %d\n", err);
 250                 return err;
 251         }
 252
 253         encoder->irq_a = gpiod_to_irq(encoder->gpio_a);
 254
 255         encoder->gpio_b = devm_gpiod_get_index(dev, NULL, 1, GPIOD_IN);
 256         if (IS_ERR(encoder->gpio_b)) {
 257                 err = PTR_ERR(encoder->gpio_b);
 258                 dev_err(dev, "unable to get GPIO at index 1: %d\n", err);
 259                 return err;
 260         }
 261
 262         encoder->irq_b = gpiod_to_irq(encoder->gpio_b);
 263
 264         input = devm_input_allocate_device(dev);
 265         if (!input)
 266                 return -ENOMEM;
 267
 268         encoder->input = input;
 269
 270         input->name = pdev->name;
 271         input->id.bustype = BUS_HOST;
 272         input->dev.parent = dev;
 273
 274         if (encoder->relative_axis)
 275                 input_set_capability(input, EV_REL, encoder->axis);
 276         else
 277                 input_set_abs_params(input,
 278                                      encoder->axis, 0, encoder->steps, 0, 1);
 279
 280         switch (steps_per_period) {
 281         case 4:
 282                 handler = &rotary_encoder_quarter_period_irq;
 283                 encoder->last_stable = rotary_encoder_get_state(encoder);
 284                 break;
 285         case 2:
 286                 handler = &rotary_encoder_half_period_irq;
 287                 encoder->last_stable = rotary_encoder_get_state(encoder);
 288                 break;
 289         case 1:
 290                 handler = &rotary_encoder_irq;
 291                 break;
 292         default:
 293                 dev_err(dev, "'%d' is not a valid steps-per-period value\n",
 294                         steps_per_period);
 295                 return -EINVAL;
 296         }
 297
 298         err = devm_request_threaded_irq(dev, encoder->irq_a, NULL, handler,
 299                                 IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING |
 300                                 IRQF_ONESHOT,
 301                                 DRV_NAME, encoder);
 302         if (err) {
 303                 dev_err(dev, "unable to request IRQ %d\n", encoder->irq_a);
 304                 return err;
 305         }
 306
 307         err = devm_request_threaded_irq(dev, encoder->irq_b, NULL, handler,
 308                                 IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING |
 309                                 IRQF_ONESHOT,
 310                                 DRV_NAME, encoder);
 311         if (err) {
 312                 dev_err(dev, "unable to request IRQ %d\n", encoder->irq_b);
 313                 return err;
 314         }
 315
 316         err = input_register_device(input);
 317         if (err) {
 318                 dev_err(dev, "failed to register input device\n");
 319                 return err;
 320         }
 321
 322         device_init_wakeup(dev,
 323                            device_property_read_bool(dev, "wakeup-source"));
 324
 325         platform_set_drvdata(pdev, encoder);
 326
 327         return 0;
 328 }
 329
 330 static int __maybe_unused rotary_encoder_suspend(struct device *dev)
 331 {
 332         struct rotary_encoder *encoder = dev_get_drvdata(dev);
 333
 334         if (device_may_wakeup(dev)) {
 335                 enable_irq_wake(encoder->irq_a);
 336                 enable_irq_wake(encoder->irq_b);
 337         }
 338
 339         return 0;
 340 }
 341
 342 static int __maybe_unused rotary_encoder_resume(struct device *dev)
 343 {
 344         struct rotary_encoder *encoder = dev_get_drvdata(dev);
 345
 346         if (device_may_wakeup(dev)) {
 347                 disable_irq_wake(encoder->irq_a);
 348                 disable_irq_wake(encoder->irq_b);
 349         }
 350
 351         return 0;
 352 }
 353
 354 static SIMPLE_DEV_PM_OPS(rotary_encoder_pm_ops,
 355                          rotary_encoder_suspend, rotary_encoder_resume);
 356
 357 #ifdef CONFIG_OF
 358 static const struct of_device_id rotary_encoder_of_match[] = {
 359         { .compatible = "rotary-encoder", },
 360         { },
 361 };
 362 MODULE_DEVICE_TABLE(of, rotary_encoder_of_match);
 363 #endif
 364
 365 static struct platform_driver rotary_encoder_driver = {
 366         .probe          = rotary_encoder_probe,
 367         .driver         = {
 368                 .name   = DRV_NAME,
 369                 .pm     = &rotary_encoder_pm_ops,
 370                 .of_match_table = of_match_ptr(rotary_encoder_of_match),
 371         }
 372 };
 373 module_platform_driver(rotary_encoder_driver);
 374
 375 MODULE_ALIAS("platform:" DRV_NAME);
 376 MODULE_DESCRIPTION("GPIO rotary encoder driver");
 377 MODULE_AUTHOR("Daniel Mack <daniel@caiaq.de>, Johan Hovold");
 378 MODULE_LICENSE("GPL v2");