最初の組み込みlinuxドライバ-LED

ドライバは次のとおりです.

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/delay.h>
#include <asm/uaccess.h>
#include <asm/irq.h>
#include <asm/io.h>
#include <mach/regs-gpio.h>
#include <mach/hardware.h>
#include <linux/device.h>//    
static struct class *first_class;
static struct class_device	*first_class_dev;
volatile unsigned long  *gpmcon=NULL;
volatile unsigned long  *gpmdat=NULL;

static int first_open(struct inode  * inode, struct file * file)
{
	//printk("open

");
	*gpmcon  &= 0xffff1111;
	return 0;
}
static ssize_t first_write(struct inode * file, const char __user *buf, size_t count, loff_t *ppos)
{
	//printk("write

");
	int val;
	copy_from_user(&val,buf,count);
	printk("val=%d
",val);
	if(val==1)
		{
			*gpmdat &=~((1<<0)|(1<<1)|(1<<2)|(1<<3));
		}
	else
		{
			*gpmdat |=(1<<0)|(1<<1)|(1<<2)|(1<<3);	
		}
	printk("gpmdatl=%d
",*gpmdat);
	return 0;
}

static struct file_operations first_openration ={
	.owner = THIS_MODULE,
	.open = first_open,
	.write = first_write,
};
int major;
static int first_init(void)
{
	//   0            
	major=register_chrdev( 0, "first",&first_openration);
	
	first_class = class_create(THIS_MODULE, "first");
	//        
	/*         class_device_create   device_create*/
	first_class_dev = device_create(first_class, NULL, MKDEV(major, 0), NULL, "xyz"); /* /dev/xyz */

	gpmcon = (volatile unsigned long*)ioremap(0x7F008820,16);//   
	gpmdat=gpmcon+1;//                  ?
						/*       unsigned long     4   */
	return 0;
}

static void first_exit(void)
{
	unregister_chrdev( major, "first");
	/*         class_device_unregister   device_unregister*/
	device_unregister(first_class_dev);
	class_destroy(first_class);
	iounmap(gpmcon);//     
}

module_init(first_init);
module_exit(first_exit);
MODULE_LICENSE("GPL");

テスト手順は次のとおりです.

#include<sys/types.h>
#include<sys/stat.h>
#include<fcntl.h>
#include<stdio.h>

int main(int argc,char **argv)
{
	int fd;
	int val=1;
	fd=open("/dev/xyz",O_RDWR);
	if(fd < 0)
		printf("can not open!!!
");
	if(argc !=2)
		{
			printf("Usage:
");
			printf("%s<on|off>
",argv[0]);
		}
	if(strcmp(argv[1],"on")==0)
		{
			val=1;
		}
	else
		{
			val=0;
		}
	write(fd,&val,4);
	printf("user val=%d

",val);
	return 0;
}

入力コマンド:./main onはすべてのランプを点灯します
   ./すべてのランプを消して