【Linux设备驱动程序（第三版）】----简单休眠 Sleepy

 【Linux设备驱动程序（第三版）】----简单休眠 Sleepy

sleepy.c

#include <linux/init.h>
#include <linux/module.h>
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/types.h>
#include <linux/fs.h>//file_operations, file
#include <linux/completion.h>
#include <asm/uaccess.h>//copy_to_user & copy_from_user
#include <linux/wait.h>

MODULE_LICENSE("Dual BSD/GPL");
#define MEMSIZE 100
int sleepy_major = 250;
DECLARE_COMPLETION(comp);
unsigned char s[MEMSIZE];
static DECLARE_WAIT_QUEUE_HEAD(wq);
static int flag = 0;

ssize_t sleepy_read(struct file *filp, char __user *buf, size_t size, loff_t *pos)
{
	unsigned long p = *pos;
	unsigned int count = size;
	int ret = 0;
	if(p >= MEMSIZE)
		return 0;
	if(count > MEMSIZE - p)
		count = MEMSIZE -p;
	wait_event_interruptible(wq, flag != 0);
	flag = 0;
	if(copy_to_user(buf, (void*)(s + p), count)){
		return -EFAULT;
	}
	*pos += count;
	ret = count;
	return ret;
}

ssize_t sleepy_write(struct file *filp, char __user *buf, size_t size, loff_t *pos)
{
	unsigned long p = *pos;
	unsigned int count = size;
	int ret = 0;

	if(p >= MEMSIZE)
		return 0;
	if(count > MEMSIZE - p)
		count = MEMSIZE -p;
	if(copy_from_user(s + p, buf, count)){
		return -EFAULT;
	}
	flag = 1;
	wake_up_interruptible(&wq);
	*pos += count;
	ret = count;
	complete(&comp);
	return ret;
}

struct file_operations sleepy_fops = {
	.owner = THIS_MODULE,
	.read = sleepy_read,
	.write = sleepy_write,
};

int sleepy_init(void)
{
	int result;

	result = register_chrdev(sleepy_major, "sleepy", &sleepy_fops);
	if(result < 0)
		return result;
	return 0;
}

void sleepy_exit(void)
{
	unregister_chrdev(sleepy_major, "sleepy");
}

module_init(sleepy_init);
module_exit(sleepy_exit);

Makefile

obj-m:= sleepy.o
modules-objs:= sleepy.o

KDIR:= /usr/src/linux-headers-2.6.31-14-generic/
PWD:= $(shell pwd)

default:
	make -C $(KDIR) M=$(PWD) modules
clean:
	rm -rf *.ko *.mod.c *.mod.o *.o *.markers *.symvers *.order

 

创建设备节点

mknod /dev/sleepy c 250 0

 

装载

insmod sleepy.ko

打开一终端，输入：

cat /dev/sleepy

此时，线程会进入休眠。

 

打开另一个终端，输入：

echo "Test" > /dev/sleepy

这个时候，上一个的读线程运行，并输出：“Test”

卸载

rmmod sleepy