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