drivers/input/misc/rotary_encoder.c

   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
  28 enum rotary_encoder_encoding {
  29         ROTENC_GRAY,
  30         ROTENC_BINARY,
  31 };
  32
  33 struct 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
  56 static 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(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
  74 static void rotary_encoder_report_event(struct rotary_encoder *encoder)
  75 {
  76         if (encoder->relative_axis) {
  77                 input_report_rel(encoder->input,
  78                                  encoder->axis, 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(encoder->input, encoder->axis, encoder->pos);
  99         }
 100
 101         input_sync(encoder->input);
 102 }
 103
 104 static irqreturn_t rotary_encoder_irq(int irq, void *dev_id)
 105 {
 106         struct rotary_encoder *encoder = dev_id;
 107         unsigned int state;
 108
 109         mutex_lock(&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         mutex_unlock(&encoder->access_mutex);
 133
 134         return IRQ_HANDLED;
 135 }
 136
 137 static irqreturn_t rotary_encoder_half_period_irq(int irq, void *dev_id)
 138 {
 139         struct rotary_encoder *encoder = dev_id;
 140         unsigned int state;
 141
 142         mutex_lock(&encoder->access_mutex);
 143
 144         state = rotary_encoder_get_state(encoder);
 145
 146         if (state & 1) {
 147                 encoder->dir = ((encoder->last_stable - state + 1) % 4) - 1;
 148         } else {
 149                 if (state != encoder->last_stable) {
 150                         rotary_encoder_report_event(encoder);
 151                         encoder->last_stable = state;
 152                 }
 153         }
 154
 155         mutex_unlock(&encoder->access_mutex);
 156
 157         return IRQ_HANDLED;
 158 }
 159
 160 static irqreturn_t rotary_encoder_quarter_period_irq(int irq, void *dev_id)
 161 {
 162         struct rotary_encoder *encoder = dev_id;
 163         unsigned int state;
 164
 165         mutex_lock(&encoder->access_mutex);
 166
 167         state = rotary_encoder_get_state(encoder);
 168
 169         if ((encoder->last_stable + 1) % 4 == state)
 170                 encoder->dir = 1;
 171         else if (encoder->last_stable == (state + 1) % 4)
 172                 encoder->dir = -1;
 173         else
 174                 goto out;
 175
 176         rotary_encoder_report_event(encoder);
 177
 178 out:
 179         encoder->last_stable = state;
 180         mutex_unlock(&encoder->access_mutex);
 181
 182         return IRQ_HANDLED;
 183 }
 184
 185 static int rotary_encoder_probe(struct platform_device *pdev)
 186 {
 187         struct device *dev = &pdev->dev;
 188         struct rotary_encoder *encoder;
 189         struct input_dev *input;
 190         irq_handler_t handler;
 191         u32 steps_per_period;
 192         unsigned int i;
 193         int err;
 194
 195         encoder = devm_kzalloc(dev, sizeof(struct rotary_encoder), GFP_KERNEL);
 196         if (!encoder)
 197                 return -ENOMEM;
 198
 199         mutex_init(&encoder->access_mutex);
 200
 201         device_property_read_u32(dev, "rotary-encoder,steps", &encoder->steps);
 202
 203         err = device_property_read_u32(dev, "rotary-encoder,steps-per-period",
 204                                        &steps_per_period);
 205         if (err) {
 206                 /*
 207                  * The 'half-period' property has been deprecated, you must
 208                  * use 'steps-per-period' and set an appropriate value, but
 209                  * we still need to parse it to maintain compatibility. If
 210                  * neither property is present we fall back to the one step
 211                  * per period behavior.
 212                  */
 213                 steps_per_period = device_property_read_bool(dev,
 214                                         "rotary-encoder,half-period") ? 2 : 1;
 215         }
 216
 217         encoder->rollover =
 218                 device_property_read_bool(dev, "rotary-encoder,rollover");
 219
 220         if (!device_property_present(dev, "rotary-encoder,encoding") ||
 221             !device_property_match_string(dev, "rotary-encoder,encoding",
 222                                           "gray")) {
 223                 dev_info(dev, "gray");
 224                 encoder->encoding = ROTENC_GRAY;
 225         } else if (!device_property_match_string(dev, "rotary-encoder,encoding",
 226                                                  "binary")) {
 227                 dev_info(dev, "binary");
 228                 encoder->encoding = ROTENC_BINARY;
 229         } else {
 230                 dev_err(dev, "unknown encoding setting\n");
 231                 return -EINVAL;
 232         }
 233
 234         device_property_read_u32(dev, "linux,axis", &encoder->axis);
 235         encoder->relative_axis =
 236                 device_property_read_bool(dev, "rotary-encoder,relative-axis");
 237
 238         encoder->gpios = devm_gpiod_get_array(dev, NULL, GPIOD_IN);
 239         if (IS_ERR(encoder->gpios)) {
 240                 err = PTR_ERR(encoder->gpios);
 241                 if (err != -EPROBE_DEFER)
 242                         dev_err(dev, "unable to get gpios: %d\n", err);
 243                 return err;
 244         }
 245         if (encoder->gpios->ndescs < 2) {
 246                 dev_err(dev, "not enough gpios found\n");
 247                 return -EINVAL;
 248         }
 249
 250         input = devm_input_allocate_device(dev);
 251         if (!input)
 252                 return -ENOMEM;
 253
 254         encoder->input = input;
 255
 256         input->name = pdev->name;
 257         input->id.bustype = BUS_HOST;
 258         input->dev.parent = dev;
 259
 260         if (encoder->relative_axis)
 261                 input_set_capability(input, EV_REL, encoder->axis);
 262         else
 263                 input_set_abs_params(input,
 264                                      encoder->axis, 0, encoder->steps, 0, 1);
 265
 266         switch (steps_per_period >> (encoder->gpios->ndescs - 2)) {
 267         case 4:
 268                 handler = &rotary_encoder_quarter_period_irq;
 269                 encoder->last_stable = rotary_encoder_get_state(encoder);
 270                 break;
 271         case 2:
 272                 handler = &rotary_encoder_half_period_irq;
 273                 encoder->last_stable = rotary_encoder_get_state(encoder);
 274                 break;
 275         case 1:
 276                 handler = &rotary_encoder_irq;
 277                 break;
 278         default:
 279                 dev_err(dev, "'%d' is not a valid steps-per-period value\n",
 280                         steps_per_period);
 281                 return -EINVAL;
 282         }
 283
 284         encoder->irq =
 285                 devm_kcalloc(dev,
 286                              encoder->gpios->ndescs, sizeof(*encoder->irq),
 287                              GFP_KERNEL);
 288         if (!encoder->irq)
 289                 return -ENOMEM;
 290
 291         for (i = 0; i < encoder->gpios->ndescs; ++i) {
 292                 encoder->irq[i] = gpiod_to_irq(encoder->gpios->desc[i]);
 293
 294                 err = devm_request_threaded_irq(dev, encoder->irq[i],
 295                                 NULL, handler,
 296                                 IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING |
 297                                 IRQF_ONESHOT,
 298                                 DRV_NAME, encoder);
 299                 if (err) {
 300                         dev_err(dev, "unable to request IRQ %d (gpio#%d)\n",
 301                                 encoder->irq[i], i);
 302                         return err;
 303                 }
 304         }
 305
 306         err = input_register_device(input);
 307         if (err) {
 308                 dev_err(dev, "failed to register input device\n");
 309                 return err;
 310         }
 311
 312         device_init_wakeup(dev,
 313                            device_property_read_bool(dev, "wakeup-source"));
 314
 315         platform_set_drvdata(pdev, encoder);
 316
 317         return 0;
 318 }
 319
 320 static int __maybe_unused rotary_encoder_suspend(struct device *dev)
 321 {
 322         struct rotary_encoder *encoder = dev_get_drvdata(dev);
 323         unsigned int i;
 324
 325         if (device_may_wakeup(dev)) {
 326                 for (i = 0; i < encoder->gpios->ndescs; ++i)
 327                         enable_irq_wake(encoder->irq[i]);
 328         }
 329
 330         return 0;
 331 }
 332
 333 static int __maybe_unused rotary_encoder_resume(struct device *dev)
 334 {
 335         struct rotary_encoder *encoder = dev_get_drvdata(dev);
 336         unsigned int i;
 337
 338         if (device_may_wakeup(dev)) {
 339                 for (i = 0; i < encoder->gpios->ndescs; ++i)
 340                         disable_irq_wake(encoder->irq[i]);
 341         }
 342
 343         return 0;
 344 }
 345
 346 static SIMPLE_DEV_PM_OPS(rotary_encoder_pm_ops,
 347                          rotary_encoder_suspend, rotary_encoder_resume);
 348
 349 #ifdef CONFIG_OF
 350 static const struct of_device_id rotary_encoder_of_match[] = {
 351         { .compatible = "rotary-encoder", },
 352         { },
 353 };
 354 MODULE_DEVICE_TABLE(of, rotary_encoder_of_match);
 355 #endif
 356
 357 static struct platform_driver rotary_encoder_driver = {
 358         .probe          = rotary_encoder_probe,
 359         .driver         = {
 360                 .name   = DRV_NAME,
 361                 .pm     = &rotary_encoder_pm_ops,
 362                 .of_match_table = of_match_ptr(rotary_encoder_of_match),
 363         }
 364 };
 365 module_platform_driver(rotary_encoder_driver);
 366
 367 MODULE_ALIAS("platform:" DRV_NAME);
 368 MODULE_DESCRIPTION("GPIO rotary encoder driver");
 369 MODULE_AUTHOR("Daniel Mack <daniel@caiaq.de>, Johan Hovold");
 370 MODULE_LICENSE("GPL v2");