char_dev_example.c

这个是linux下的一个字符设备的驱动程序

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <asm/uaccess.h>
#include <asm/arch-s3c2410/regs-serial.h>
#include <asm/io.h>
#include <linux/slab.h>

#define SYSCFG S3C24XX_VA_UART1 
#define UART_ULCON (*((volatile unsigned *)(SYSCFG + 0x00)) )
#define UART_UCON (*((volatile unsigned *)(SYSCFG + 0x04)) )
#define UART_UTRSTAT (*((volatile unsigned *)(SYSCFG + 0x10)) )
#define UART_UTXH (*((volatile unsigned *)(SYSCFG + 0x20)) )
#define UART_URXH  (*((volatile unsigned *)(SYSCFG + 0x24) ))
#define UART_UBRDIV (*((volatile unsigned *)(SYSCFG + 0x28) ))
#define GET_CHAR() (*((volatile unsigned *)(SYSCFG + 0x24)))
#define PUT_CHAR(c) (*((volatile unsigned *)(SYSCFG + 0x20)) = (unsigned)(c))

#define AKAE_MAJOR 240

MODULE_AUTHOR("Huyongfu");
MODULE_DESCRIPTION("module example");
MODULE_LICENSE("GPL");

ssize_t akae_read(struct file *filp,char __user *buf,size_t count,loff_t *f_pos)
{
	int i = 0;
	char *head = (char *)kmalloc(count,GFP_KERNEL);
	char *p = head;;
	while (i < count)
	{
		if ((UART_UTRSTAT & 0x01)== 0x01)
		{
			p[i++] = GET_CHAR();
		}
		else
		{
			set_current_state(TASK_INTERRUPTIBLE);
			schedule_timeout(10);
		}
	}
	p[i] = 0;
	copy_to_user(buf,head,count);
	kfree(p);

	return count;
}

ssize_t akae_write(struct file *filp,const char __user *buf,size_t count,loff_t *f_ops)
{
	int i = 0;
	char *head = (char *)kmalloc(count,GFP_KERNEL);
	char *p = head;;

	copy_from_user(head,buf,count);

	while (i < count)
	{
		if ((UART_UTRSTAT & 0x02) == 0x02)
		{
			PUT_CHAR(p[i++]);
		}
		else
		{
			set_current_state(TASK_INTERRUPTIBLE);
			schedule_timeout(1 * HZ);
		}
	}

	kfree(p);

	return i;
}

int akae_release(struct inode *inode,struct file *filp)
{
	return 0;
}

struct file_operations akae_fops = {
	.owner = THIS_MODULE,
	.read = akae_read,
	.write = akae_write,
	.release = akae_release,
};

	int __init
akae_init(void)
{
	int rc;
	printk("Test char dev\n");

	UART_UCON |= 0x05;
	UART_ULCON |= 0x03;
	UART_UBRDIV = 26; /* (int)(50000000 / (115200 * 16)) -1 = 26 */

	rc = register_chrdev(AKAE_MAJOR,"akae",&akae_fops);
	if (rc < 0)
	{
		printk("register %s char dev error\n","akae");
		return -1;
	}

	printk("ok\n");
	return 0;
}

	void __exit
akae_exit(void)
{
	unregister_chrdev(AKAE_MAJOR,"akae");
	printk("module exit\n");
	return ;
}

module_init(akae_init);
module_exit(akae_exit);