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