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