drivers/input/misc/rotary_encoder.c

   1 /*
   2  * rotary_encoder.c
   3  *
   4  * (c) 2009 Daniel Mack <daniel@caiaq.de>
   5  *
   6  * state machine code inspired by code from Tim Ruetz
   7  *
   8  * A generic driver for rotary encoders connected to GPIO lines.
   9  * See file:Documentation/input/rotary_encoder.txt for more information
  10  *
  11  * This program is free software; you can redistribute it and/or modify
  12  * it under the terms of the GNU General Public License version 2 as
  13  * published by the Free Software Foundation.
  14  */
  15
  16 #include <linux/kernel.h>
  17 #include <linux/module.h>
  18 #include <linux/init.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.h>
  24 #include <linux/rotary_encoder.h>
  25 #include <linux/slab.h>
  26
  27 #define DRV_NAME "rotary-encoder"
  28
  29 struct rotary_encoder {
  30         struct input_dev *input;
  31         struct rotary_encoder_platform_data *pdata;
  32
  33         unsigned int axis;
  34         unsigned int pos;
  35
  36         unsigned int irq_a;
  37         unsigned int irq_b;
  38
  39         bool armed;
  40         unsigned char dir;      /* 0 - clockwise, 1 - CCW */
  41 };
  42
  43 static irqreturn_t rotary_encoder_irq(int irq, void *dev_id)
  44 {
  45         struct rotary_encoder *encoder = dev_id;
  46         struct rotary_encoder_platform_data *pdata = encoder->pdata;
  47         int a = !!gpio_get_value(pdata->gpio_a);
  48         int b = !!gpio_get_value(pdata->gpio_b);
  49         int state;
  50
  51         a ^= pdata->inverted_a;
  52         b ^= pdata->inverted_b;
  53         state = (a << 1) | b;
  54
  55         switch (state) {
  56
  57         case 0x0:
  58                 if (!encoder->armed)
  59                         break;
  60
  61                 if (pdata->relative_axis) {
  62                         input_report_rel(encoder->input, pdata->axis,
  63                                          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                         if (pdata->rollover)
  79                                 pos %= pdata->steps;
  80                         encoder->pos = pos;
  81                         input_report_abs(encoder->input, pdata->axis,
  82                                          encoder->pos);
  83                 }
  84                 input_sync(encoder->input);
  85
  86                 encoder->armed = false;
  87                 break;
  88
  89         case 0x1:
  90         case 0x2:
  91                 if (encoder->armed)
  92                         encoder->dir = state - 1;
  93                 break;
  94
  95         case 0x3:
  96                 encoder->armed = true;
  97                 break;
  98         }
  99
 100         return IRQ_HANDLED;
 101 }
 102
 103 static int __devinit rotary_encoder_probe(struct platform_device *pdev)
 104 {
 105         struct rotary_encoder_platform_data *pdata = pdev->dev.platform_data;
 106         struct rotary_encoder *encoder;
 107         struct input_dev *input;
 108         int err;
 109
 110         if (!pdata) {
 111                 dev_err(&pdev->dev, "missing platform data\n");
 112                 return -ENOENT;
 113         }
 114
 115         encoder = kzalloc(sizeof(struct rotary_encoder), GFP_KERNEL);
 116         input = input_allocate_device();
 117         if (!encoder || !input) {
 118                 dev_err(&pdev->dev, "failed to allocate memory for device\n");
 119                 err = -ENOMEM;
 120                 goto exit_free_mem;
 121         }
 122
 123         encoder->input = input;
 124         encoder->pdata = pdata;
 125         encoder->irq_a = gpio_to_irq(pdata->gpio_a);
 126         encoder->irq_b = gpio_to_irq(pdata->gpio_b);
 127
 128         /* create and register the input driver */
 129         input->name = pdev->name;
 130         input->id.bustype = BUS_HOST;
 131         input->dev.parent = &pdev->dev;
 132
 133         if (pdata->relative_axis) {
 134                 input->evbit[0] = BIT_MASK(EV_REL);
 135                 input->relbit[0] = BIT_MASK(pdata->axis);
 136         } else {
 137                 input->evbit[0] = BIT_MASK(EV_ABS);
 138                 input_set_abs_params(encoder->input,
 139                                      pdata->axis, 0, pdata->steps, 0, 1);
 140         }
 141
 142         err = input_register_device(input);
 143         if (err) {
 144                 dev_err(&pdev->dev, "failed to register input device\n");
 145                 goto exit_free_mem;
 146         }
 147
 148         /* request the GPIOs */
 149         err = gpio_request(pdata->gpio_a, DRV_NAME);
 150         if (err) {
 151                 dev_err(&pdev->dev, "unable to request GPIO %d\n",
 152                         pdata->gpio_a);
 153                 goto exit_unregister_input;
 154         }
 155
 156         err = gpio_direction_input(pdata->gpio_a);
 157         if (err) {
 158                 dev_err(&pdev->dev, "unable to set GPIO %d for input\n",
 159                         pdata->gpio_a);
 160                 goto exit_unregister_input;
 161         }
 162
 163         err = gpio_request(pdata->gpio_b, DRV_NAME);
 164         if (err) {
 165                 dev_err(&pdev->dev, "unable to request GPIO %d\n",
 166                         pdata->gpio_b);
 167                 goto exit_free_gpio_a;
 168         }
 169
 170         err = gpio_direction_input(pdata->gpio_b);
 171         if (err) {
 172                 dev_err(&pdev->dev, "unable to set GPIO %d for input\n",
 173                         pdata->gpio_b);
 174                 goto exit_free_gpio_a;
 175         }
 176
 177         /* request the IRQs */
 178         err = request_irq(encoder->irq_a, &rotary_encoder_irq,
 179                           IORESOURCE_IRQ_HIGHEDGE | IORESOURCE_IRQ_LOWEDGE,
 180                           DRV_NAME, encoder);
 181         if (err) {
 182                 dev_err(&pdev->dev, "unable to request IRQ %d\n",
 183                         encoder->irq_a);
 184                 goto exit_free_gpio_b;
 185         }
 186
 187         err = request_irq(encoder->irq_b, &rotary_encoder_irq,
 188                           IORESOURCE_IRQ_HIGHEDGE | IORESOURCE_IRQ_LOWEDGE,
 189                           DRV_NAME, encoder);
 190         if (err) {
 191                 dev_err(&pdev->dev, "unable to request IRQ %d\n",
 192                         encoder->irq_b);
 193                 goto exit_free_irq_a;
 194         }
 195
 196         platform_set_drvdata(pdev, encoder);
 197
 198         return 0;
 199
 200 exit_free_irq_a:
 201         free_irq(encoder->irq_a, encoder);
 202 exit_free_gpio_b:
 203         gpio_free(pdata->gpio_b);
 204 exit_free_gpio_a:
 205         gpio_free(pdata->gpio_a);
 206 exit_unregister_input:
 207         input_unregister_device(input);
 208         input = NULL; /* so we don't try to free it */
 209 exit_free_mem:
 210         input_free_device(input);
 211         kfree(encoder);
 212         return err;
 213 }
 214
 215 static int __devexit rotary_encoder_remove(struct platform_device *pdev)
 216 {
 217         struct rotary_encoder *encoder = platform_get_drvdata(pdev);
 218         struct rotary_encoder_platform_data *pdata = pdev->dev.platform_data;
 219
 220         free_irq(encoder->irq_a, encoder);
 221         free_irq(encoder->irq_b, encoder);
 222         gpio_free(pdata->gpio_a);
 223         gpio_free(pdata->gpio_b);
 224         input_unregister_device(encoder->input);
 225         platform_set_drvdata(pdev, NULL);
 226         kfree(encoder);
 227
 228         return 0;
 229 }
 230
 231 static struct platform_driver rotary_encoder_driver = {
 232         .probe          = rotary_encoder_probe,
 233         .remove         = __devexit_p(rotary_encoder_remove),
 234         .driver         = {
 235                 .name   = DRV_NAME,
 236                 .owner  = THIS_MODULE,
 237         }
 238 };
 239
 240 static int __init rotary_encoder_init(void)
 241 {
 242         return platform_driver_register(&rotary_encoder_driver);
 243 }
 244
 245 static void __exit rotary_encoder_exit(void)
 246 {
 247         platform_driver_unregister(&rotary_encoder_driver);
 248 }
 249
 250 module_init(rotary_encoder_init);
 251 module_exit(rotary_encoder_exit);
 252
 253 MODULE_ALIAS("platform:" DRV_NAME);
 254 MODULE_DESCRIPTION("GPIO rotary encoder driver");
 255 MODULE_AUTHOR("Daniel Mack <daniel@caiaq.de>");
 256 MODULE_LICENSE("GPL v2");
 257