【Linux设备驱动程序（第三版）】----简单休眠 Sleepy

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【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 100int 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.omodules-objs:= sleepy.oKDIR:= /usr/src/linux-headers-2.6.31-14-generic/PWD:= $(shell pwd)default:make -C $(KDIR) M=$(PWD) modulesclean: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