scoutos / scout_gumstix / encoder / encoder.c @ f024710b
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#include <linux/init.h> |
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#include <linux/module.h> |
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#include <linux/fs.h> |
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#include <linux/cdev.h> |
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#include <linux/slab.h> |
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#include <linux/device.h> |
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#include <linux/semaphore.h> |
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#include <linux/interrupt.h> |
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#include <linux/gpio.h> |
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#include <asm/uaccess.h> |
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|
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MODULE_AUTHOR("Tom Mullins");
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MODULE_LICENSE("GPL");
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|
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#define BUF_LEN 20 |
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#define N_ENCODERS 4 |
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const int enc_pins[N_ENCODERS][2] = {{78, 79}, {80, 81}, {82, 83}, {84, 85}}; |
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struct class *enc_class = NULL; |
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dev_t first_dev; |
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|
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struct enc_t
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{ |
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char buf[BUF_LEN+1]; |
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struct cdev cdev;
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struct semaphore sem;
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struct device *device;
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int irq[2]; |
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int status;
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atomic_t value; |
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dev_t dev; |
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} |
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encs[N_ENCODERS]; |
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|
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static int enc_open(struct inode *inode, struct file *file); |
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static ssize_t enc_read(struct file *file, char __user *udata, size_t count, |
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loff_t *offset); |
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static ssize_t enc_write(struct file *file, const char __user *udata, |
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size_t count, loff_t *offset); |
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static void enc_free(struct enc_t *enc); |
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static int enc_init(dev_t dev, struct enc_t *enc); |
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|
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struct file_operations fops =
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{ |
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.owner = THIS_MODULE, |
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.open = enc_open, |
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.read = enc_read, |
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.write = enc_write |
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}; |
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|
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static int enc_open(struct inode *inode, struct file *file) |
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{ |
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int i = iminor(inode);
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if (i < 0 || i >= N_ENCODERS) |
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{ |
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return -ENXIO;
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} |
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file->private_data = &encs[i]; |
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return 0; |
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} |
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|
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static ssize_t enc_read(struct file *file, char __user *udata, size_t count, |
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loff_t *offset) |
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{ |
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int len;
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struct enc_t *enc = file->private_data;
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if (down_interruptible(&enc->sem))
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{ |
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return -ERESTARTSYS;
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} |
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len = snprintf(enc->buf, BUF_LEN+1, "%d\n", atomic_read(&enc->value)); |
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if (*offset > len)
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{ |
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return 0; |
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} |
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len -= *offset; |
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if (len > count)
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{ |
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len = count; |
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} |
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copy_to_user(udata, enc->buf + *offset, len); |
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*offset += len; |
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up(&enc->sem); |
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return len;
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} |
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|
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static ssize_t enc_write(struct file *file, const char __user *udata, |
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size_t count, loff_t *offset) |
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{ |
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char *end;
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int new_value;
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struct enc_t *enc = file->private_data;
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if (down_interruptible(&enc->sem))
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{ |
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return -ERESTARTSYS;
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} |
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if (count > BUF_LEN)
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{ |
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count = BUF_LEN; |
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} |
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copy_from_user(enc->buf, udata, count); |
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enc->buf[count] = '\0';
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new_value = simple_strtoi(enc->buf, &end, 10);
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atomic_set(&enc->value, new_value); |
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*offset += count; |
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up(&enc->sem); |
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return count;
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} |
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irqreturn_t intA(int irq, void *enc, struct pt_regs *regs) { |
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int this = gpio_get_value(enc->pins[0]); |
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int other = gpio_get_value(enc->pins[1]); |
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if (this == other) {
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atomic_inc(&enc->value); |
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} else {
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atomic_dec(&enc->value); |
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} |
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return IRQ_HANDLED;
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} |
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irqreturn_t intB(int irq, void *enc, struct pt_regs *regs) { |
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int this = gpio_get_value(enc->pins[1]); |
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int other = gpio_get_value(enc->pins[0]); |
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if (this == other) {
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atomic_dec(&enc->value); |
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} else {
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atomic_inc(&enc->value); |
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} |
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return IRQ_HANDLED;
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} |
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static int enc_init(dev_t dev, struct enc_t *enc, int *pins) |
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{ |
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int err, i;
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// initialize members
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cdev_init(&enc->cdev, &fops); |
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enc->cdev.owner = THIS_MODULE; |
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enc->dev = dev; |
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enc->status = 0;
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sema_init(&enc->sem, 1);
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// make cdev file operations accessible
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err = cdev_add(&enc->cdev, enc->dev, N_ENCODERS); |
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if (err)
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{ |
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enc_free(enc); |
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return err;
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} |
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enc->status = 1;
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// register gpio and interrupts
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for (i = 0; i < 2; i++) { |
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enc->pins[i] = pins[i]; |
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enc->irq[i] = gpio_to_irq(pins[i]); |
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if (enc->irq[i] < 0) { |
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printk("Error %d requesting irq number for gpio %d\n", enc->irq[i],
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enc->pins[i]); |
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return 1; |
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} |
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err = gpio_direction_input(enc->pins[i]); |
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if (err < 0) { |
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printk("Error %d setting gpio %d to input\n", err, enc->pins[i]);
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return 1; |
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} |
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err = request_irq(enc->irq[i], i? intB : intA, SA_INTERRUPT, "encoder", enc);
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if (err < 0) { |
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printk("Error %d requesting irq %d\n", err, enc->irq[i]);
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return 1; |
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} |
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// TODO the error checking here does not properly clean up after itself
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// TODO perhaps we should use gpio_request? probably not necessary...
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} |
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enc->status = 2;
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return 0; |
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} |
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int enc_create_dev(struct enc_t *enc) { |
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// make file in /dev
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enc->device = device_create(enc_class, NULL, enc->dev, NULL, "enc%d", |
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MINOR(enc->dev)); |
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if (IS_ERR(enc->device))
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{ |
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err = PTR_ERR(enc->device); |
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enc->device = NULL;
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enc_free(enc); |
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return err;
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} |
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enc->status = 3;
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return 0; |
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} |
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static void enc_free(struct enc_t *enc) |
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{ |
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switch (enc->status)
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{ |
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case 3: |
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device_destroy(enc_class, enc->dev); |
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enc->device = NULL;
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case 2: |
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free_irq(enc->irq[0], enc);
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free_irq(enc->irq[1], enc);
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case 1: |
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cdev_del(&enc->cdev); |
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} |
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enc->status = 0;
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} |
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static void enc_exit_module(void) |
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{ |
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int i;
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for (i = 0; i < N_ENCODERS; i++) |
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{ |
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enc_free(&encs[i]); |
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} |
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if (enc_class) {
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class_destroy(enc_class); |
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enc_class = NULL;
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} |
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unregister_chrdev_region(first_dev, N_ENCODERS); |
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} |
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module_exit(enc_exit_module); |
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static int __init enc_init_module(void) |
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{ |
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int i, err;
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// allocate character devices and get major number
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err = alloc_chrdev_region(&first_dev, 0, N_ENCODERS, "encoder"); |
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if (err)
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{ |
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printk(KERN_ALERT "Error %d in alloc_chrdev_region\n", err);
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return 1; |
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} |
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// initialize enc structures
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for (i = 0; i < N_ENCODERS; i++) { |
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err = enc_init(first_dev + i, &encs[i], enc_pins[i]); |
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if (err)
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{ |
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printk(KERN_WARNING "Error %d initializing encoder %d\n", err, i);
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enc_exit_module(); |
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return 1; |
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} |
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} |
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// register our device class for files in /dev
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enc_class = class_create(THIS_MODULE, "encoder");
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if (IS_ERR(enc_class))
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{ |
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err = PTR_ERR(enc_class); |
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enc_class = NULL;
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printk(KERN_WARNING "Error %d creating device class\n", err);
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} |
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else
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{ |
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// create each device
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for (i = 0; i < N_ENCODERS; i++) { |
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err = enc_create_dev(&encs[i]); |
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if (err)
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{ |
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printk(KERN_WARNING "Error %d creating enc%d\n", err, i);
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enc_exit_module(); |
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return 1; |
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} |
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} |
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} |
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return 0; |
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} |
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module_init(enc_init_module); |