tesled.c

這是一個AT91開發版程式碼 對MCU有興趣可以研究

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/fs.h>
#include <asm/uaccess.h> /* get_user and put_user */
#include <asm/arch/gpio.h>

/* #define DEBUG */

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Nelson Castillo/emQbit");

#define SUCCESS 0
#define DEVICE_FILE_NAME "tesled"
#define DEVICE_NAME "tesled"
#define MAJOR_NUM 101

struct semaphore sw_sem;

#define led_bit0    AT91_PIN_PC21 /* led */

unsigned char led_state = 0;
int default_led_state = 1;

module_param(default_led_state, int, 0);

int
set_led_state(unsigned char s)
{

  if (s <= 1)
  {
    at91_set_gpio_value(led_bit0, s & 0x1);

#ifdef DEBUG
    printk(KERN_INFO "bit0: %x\n", s);
#endif

    led_state = s;
    return 0;
  }

  return -1; /* error */
}

static int device_open(struct inode *inode, struct file *file)
{

#ifdef DEBUG
  printk(KERN_INFO "device_open(%p)\n", file);
#endif

  return SUCCESS;
}

static int device_release(struct inode *inode, struct file *file)
{
#ifdef DEBUG
  printk(KERN_INFO "device_release(%p,%p)\n", inode, file);
#endif

  return SUCCESS;
}

static ssize_t device_read(struct file *file,
                           char __user * buffer,
                           size_t length,
                           loff_t * offset)
{
  unsigned char value = led_state;
  int ret_val = 0;

  if (down_interruptible (&sw_sem))
      return -ERESTARTSYS;

#ifdef DEBUG
  printk(KERN_INFO "device_read(%p,%p,%d)\n", file, buffer, length);
#endif

  if (put_user(value, buffer))
  {
    ret_val = -EFAULT;
    goto read_exit;
  }

  ret_val++;

  read_exit:
  up(&sw_sem);
  return ret_val;
}

static ssize_t
device_write(struct file *file,
             const char __user * buffer, size_t length, loff_t * offset)
{
  unsigned char value;
  int  ret_val = 0;

  if (down_interruptible (&sw_sem))
      return -ERESTARTSYS;

#ifdef DEBUG
  printk(KERN_INFO "device_write(%p,%p,%d,%d)\n", file, buffer, length, *offset);
#endif

  if (get_user(value, buffer))
  {
    ret_val = -EFAULT;
    goto write_out;
  }

  if (set_led_state(value))
  {
    ret_val = -EINVAL;
    goto write_out;
  }

  ret_val++;

#ifdef DEBUG
  printk(KERN_INFO "wrote %x\n", value);
#endif

write_out:

  up(&sw_sem);
  return ret_val;
}

struct file_operations our_file_ops = {
  .read = device_read,
  .write = device_write,
  .open = device_open,
  .release = device_release,
  .owner = THIS_MODULE,
};

int init_module()
{
  int ret_val;

  ret_val = register_chrdev(MAJOR_NUM, DEVICE_NAME, &our_file_ops);

  if (ret_val < 0)
  {
    printk(KERN_ALERT "device %s failed(%d)\n", DEVICE_NAME, ret_val);
    return ret_val;
  }

  sema_init(&sw_sem, 1);

  at91_set_gpio_output(led_bit0, 0);

  printk(KERN_INFO "mknod %s c %d 0\n", DEVICE_FILE_NAME, MAJOR_NUM);

  if (set_led_state(default_led_state))
    printk(KERN_INFO "invalid default_led_state\n");

  return SUCCESS;
}

void cleanup_module()
{
  int ret;

  ret = unregister_chrdev(MAJOR_NUM, DEVICE_NAME);

  if (ret < 0)
    printk(KERN_ALERT "Error: unregister_chrdev: %d\n", ret);
}