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"); 221 222