#include <linux/module.h>
#include <linux/fs.h>
#include <linux/sched.h>
#include "ioctl_led.h"
#define DEV_NAME "test-dev"
volatile bool empty = true;
//定义一个进程资源的指针变量
struct task_struct *task;
int test_open(struct inode *inode, struct file *filp)
{
printk("test open\n");
return 0;
}
int test_close(struct inode *inode, struct file *filp)
{
printk("test close\n");
return 0;
}
ssize_t test_read(struct file *filp, char __user *buf, size_t size, loff_t *off)
{
int ret;
//如果为真，那么就开始读
while(empty)
{
//f_flags 指的是对应open调用的时候所指定的flag
//O_NONBLOCK 非阻塞形式打开
if(filp->f_flags & O_NONBLOCK)
{
return 0;
}
//current (指向当前进程的task_struct)
//(内核栈的底部thread_info.task)
task = current;
//设置当前进程的状态为TASK_INTERRUPTIBLE
//TASK_INTERRUPTIBLE是阻塞态，进程当前正在等待除CPU外的其他系统资源,可以被信号唤醒.
set_current_state(TASK_INTERRUPTIBLE);
//通知调度器执行调度。
schedule();
if(signal_pending(current))
return -ERESTARTSYS;
// return -EAGAIN;
printk("read: wake up\n");
}
ret = size;
empty = true;
return ret;
}
ssize_t test_write(struct file *filp, const char __user *buf, size_t size, loff_t *off)
{
int ret;
empty = false;
wake_up_process(task);
ret = size;
return ret;
}
int major = 0;
struct file_operations fops = {
.open = test_open,
.release = test_close,
.read = test_read,
.write = test_write,
};
//模块;
int test_init(void)
{
int ret;
printk("test init\n");
//注册一个字符设备驱动
ret = register_chrdev(major, DEV_NAME, &fops);
if(ret < 0)
return ret;
else
{
if(0 == major)
{
major = ret;
printk("major = %d\n", major);
}
}
return 0;
}
void test_exit(void)
{
printk("test exit\n");
//撤销字符设备
unregister_chrdev(major, DEV_NAME);
}
module_init(test_init);
module_exit(test_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("yang.yx");
MODULE_VERSION("1.1");
Makefile
obj-m += test.o ROOTFS = /rootfs KERNEL_SRC = /lib/modules/`uname -r`/build all: make -C $(KERNEL_SRC) M=`pwd` modules clean: make -C $(KERNEL_SRC) M=`pwd` clean rm -rf app install: make -C $(KERNEL_SRC) M=`pwd` modules_install INSTALL_MOD_PATH=$(ROOTFS) app: arm-linux-gcc app.c -o appioctl.c
#ifndef __IOCTL_H__ #define __IOCTL_H__ #include <linux/ioctl.h> #define LED_TYPE 0x1 #define LED_ALLON _IO(LED_TYPE, 0) #define LED_ALLOFF _IO(LED_TYPE, 1) #define LED_ON _IOW(LED_TYPE, 2, int) #define LED_OFF _IOW(LED_TYPE, 3, int) #endif
