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/init.h>
  20 #include <linux/interrupt.h>
  21 #include <linux/input.h>
  22 #include <linux/device.h>
  23 #include <linux/platform_device.h>
  24 #include <linux/gpio.h>
  25 #include <linux/rotary_encoder.h>
  26 #include <linux/slab.h>
  27
  28 #define DRV_NAME "rotary-encoder"
  29
  30 struct rotary_encoder {
  31         struct input_dev *input;
  32         struct rotary_encoder_platform_data *pdata;
  33
  34         unsigned int axis;
  35         unsigned int pos;
  36
  37         unsigned int irq_a;
  38         unsigned int irq_b;
  39
  40         bool armed;
  41         unsigned char dir;      /* 0 - clockwise, 1 - CCW */
  42
  43         char last_stable;
  44 };
  45
  46 static int rotary_encoder_get_state(struct rotary_encoder_platform_data *pdata)
  47 {
  48         int a = !!gpio_get_value(pdata->gpio_a);
  49         int b = !!gpio_get_value(pdata->gpio_b);
  50
  51         a ^= pdata->inverted_a;
  52         b ^= pdata->inverted_b;
  53
  54         return ((a << 1) | b);
  55 }
  56
  57 static void rotary_encoder_report_event(struct rotary_encoder *encoder)
  58 {
  59         struct rotary_encoder_platform_data *pdata = encoder->pdata;
  60
  61         if (pdata->relative_axis) {
  62                 input_report_rel(encoder->input,
  63                                  pdata->axis, encoder->dir ? -1 : 1);
  64         } else {
  65                 unsigned int pos = encoder->pos;
  66
  67                 if (encoder->dir) {
  68                         /* turning counter-clockwise */
  69                         if (pdata->rollover)
  70                                 pos += pdata->steps;
  71                         if (pos)
  72                                 pos--;
  73                 } else {
  74                         /* turning clockwise */
  75                         if (pdata->rollover || pos < pdata->steps)
  76                                 pos++;
  77                 }
  78
  79                 if (pdata->rollover)
  80                         pos %= pdata->steps;
  81
  82                 encoder->pos = pos;
  83                 input_report_abs(encoder->input, pdata->axis, encoder->pos);
  84         }
  85
  86         input_sync(encoder->input);
  87 }
  88
  89 static irqreturn_t rotary_encoder_irq(int irq, void *dev_id)
  90 {
  91         struct rotary_encoder *encoder = dev_id;
  92         int state;
  93
  94         state = rotary_encoder_get_state(encoder->pdata);
  95
  96         switch (state) {
  97         case 0x0:
  98                 if (encoder->armed) {
  99                         rotary_encoder_report_event(encoder);
 100                         encoder->armed = false;
 101                 }
 102                 break;
 103
 104         case 0x1:
 105         case 0x2:
 106                 if (encoder->armed)
 107                         encoder->dir = state - 1;
 108                 break;
 109
 110         case 0x3:
 111                 encoder->armed = true;
 112                 break;
 113         }
 114
 115         return IRQ_HANDLED;
 116 }
 117
 118 static irqreturn_t rotary_encoder_half_period_irq(int irq, void *dev_id)
 119 {
 120         struct rotary_encoder *encoder = dev_id;
 121         int state;
 122
 123         state = rotary_encoder_get_state(encoder->pdata);
 124
 125         switch (state) {
 126         case 0x00:
 127         case 0x03:
 128                 if (state != encoder->last_stable) {
 129                         rotary_encoder_report_event(encoder);
 130                         encoder->last_stable = state;
 131                 }
 132                 break;
 133
 134         case 0x01:
 135         case 0x02:
 136                 encoder->dir = (encoder->last_stable + state) & 0x01;
 137                 break;
 138         }
 139
 140         return IRQ_HANDLED;
 141 }
 142
 143 static int __devinit rotary_encoder_probe(struct platform_device *pdev)
 144 {
 145         struct rotary_encoder_platform_data *pdata = pdev->dev.platform_data;
 146         struct rotary_encoder *encoder;
 147         struct input_dev *input;
 148         irq_handler_t handler;
 149         int err;
 150
 151         if (!pdata) {
 152                 dev_err(&pdev->dev, "missing platform data\n");
 153                 return -ENOENT;
 154         }
 155
 156         encoder = kzalloc(sizeof(struct rotary_encoder), GFP_KERNEL);
 157         input = input_allocate_device();
 158         if (!encoder || !input) {
 159                 dev_err(&pdev->dev, "failed to allocate memory for device\n");
 160                 err = -ENOMEM;
 161                 goto exit_free_mem;
 162         }
 163
 164         encoder->input = input;
 165         encoder->pdata = pdata;
 166         encoder->irq_a = gpio_to_irq(pdata->gpio_a);
 167         encoder->irq_b = gpio_to_irq(pdata->gpio_b);
 168
 169         /* create and register the input driver */
 170         input->name = pdev->name;
 171         input->id.bustype = BUS_HOST;
 172         input->dev.parent = &pdev->dev;
 173
 174         if (pdata->relative_axis) {
 175                 input->evbit[0] = BIT_MASK(EV_REL);
 176                 input->relbit[0] = BIT_MASK(pdata->axis);
 177         } else {
 178                 input->evbit[0] = BIT_MASK(EV_ABS);
 179                 input_set_abs_params(encoder->input,
 180                                      pdata->axis, 0, pdata->steps, 0, 1);
 181         }
 182
 183         err = input_register_device(input);
 184         if (err) {
 185                 dev_err(&pdev->dev, "failed to register input device\n");
 186                 goto exit_free_mem;
 187         }
 188
 189         /* request the GPIOs */
 190         err = gpio_request(pdata->gpio_a, DRV_NAME);
 191         if (err) {
 192                 dev_err(&pdev->dev, "unable to request GPIO %d\n",
 193                         pdata->gpio_a);
 194                 goto exit_unregister_input;
 195         }
 196
 197         err = gpio_direction_input(pdata->gpio_a);
 198         if (err) {
 199                 dev_err(&pdev->dev, "unable to set GPIO %d for input\n",
 200                         pdata->gpio_a);
 201                 goto exit_unregister_input;
 202         }
 203
 204         err = gpio_request(pdata->gpio_b, DRV_NAME);
 205         if (err) {
 206                 dev_err(&pdev->dev, "unable to request GPIO %d\n",
 207                         pdata->gpio_b);
 208                 goto exit_free_gpio_a;
 209         }
 210
 211         err = gpio_direction_input(pdata->gpio_b);
 212         if (err) {
 213                 dev_err(&pdev->dev, "unable to set GPIO %d for input\n",
 214                         pdata->gpio_b);
 215                 goto exit_free_gpio_a;
 216         }
 217
 218         /* request the IRQs */
 219         if (pdata->half_period) {
 220                 handler = &rotary_encoder_half_period_irq;
 221                 encoder->last_stable = rotary_encoder_get_state(pdata);
 222         } else {
 223                 handler = &rotary_encoder_irq;
 224         }
 225
 226         err = request_irq(encoder->irq_a, handler,
 227                           IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING,
 228                           DRV_NAME, encoder);
 229         if (err) {
 230                 dev_err(&pdev->dev, "unable to request IRQ %d\n",
 231                         encoder->irq_a);
 232                 goto exit_free_gpio_b;
 233         }
 234
 235         err = request_irq(encoder->irq_b, handler,
 236                           IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING,
 237                           DRV_NAME, encoder);
 238         if (err) {
 239                 dev_err(&pdev->dev, "unable to request IRQ %d\n",
 240                         encoder->irq_b);
 241                 goto exit_free_irq_a;
 242         }
 243
 244         platform_set_drvdata(pdev, encoder);
 245
 246         return 0;
 247
 248 exit_free_irq_a:
 249         free_irq(encoder->irq_a, encoder);
 250 exit_free_gpio_b:
 251         gpio_free(pdata->gpio_b);
 252 exit_free_gpio_a:
 253         gpio_free(pdata->gpio_a);
 254 exit_unregister_input:
 255         input_unregister_device(input);
 256         input = NULL; /* so we don't try to free it */
 257 exit_free_mem:
 258         input_free_device(input);
 259         kfree(encoder);
 260         return err;
 261 }
 262
 263 static int __devexit rotary_encoder_remove(struct platform_device *pdev)
 264 {
 265         struct rotary_encoder *encoder = platform_get_drvdata(pdev);
 266         struct rotary_encoder_platform_data *pdata = pdev->dev.platform_data;
 267
 268         free_irq(encoder->irq_a, encoder);
 269         free_irq(encoder->irq_b, encoder);
 270         gpio_free(pdata->gpio_a);
 271         gpio_free(pdata->gpio_b);
 272         input_unregister_device(encoder->input);
 273         platform_set_drvdata(pdev, NULL);
 274         kfree(encoder);
 275
 276         return 0;
 277 }
 278
 279 static struct platform_driver rotary_encoder_driver = {
 280         .probe          = rotary_encoder_probe,
 281         .remove         = __devexit_p(rotary_encoder_remove),
 282         .driver         = {
 283                 .name   = DRV_NAME,
 284                 .owner  = THIS_MODULE,
 285         }
 286 };
 287
 288 static int __init rotary_encoder_init(void)
 289 {
 290         return platform_driver_register(&rotary_encoder_driver);
 291 }
 292
 293 static void __exit rotary_encoder_exit(void)
 294 {
 295         platform_driver_unregister(&rotary_encoder_driver);
 296 }
 297
 298 module_init(rotary_encoder_init);
 299 module_exit(rotary_encoder_exit);
 300
 301 MODULE_ALIAS("platform:" DRV_NAME);
 302 MODULE_DESCRIPTION("GPIO rotary encoder driver");
 303 MODULE_AUTHOR("Daniel Mack <daniel@caiaq.de>, Johan Hovold");
 304 MODULE_LICENSE("GPL v2");