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/devices/rotary-encoder.rst 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_kcalloc(dev,
 287                              encoder->gpios->ndescs, sizeof(*encoder->irq),
 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");