驱动：
#include <linux/module.h>
#include <linux/types.h>
#include <linux/fs.h>
#include <linux/errno.h>
#include <linux/mm.h>
#include <linux/sched.h>
#include <linux/init.h>
#include <linux/cdev.h>
#include <asm/io.h>
#include <asm/system.h>
#include <asm/uaccess.h>
#include <linux/poll.h>
#define GLOBALFIFO_SIZE 0x1000
#define FIFO_CLEAR 0x1
#define GLOBALFIFO_MAJOR 253
static int globalfifo_major = GLOBALFIFO_MAJOR;
struct globalfifo_dev
{
struct cdev cdev;
unsigned int current_len;
unsigned char mem[GLOBALFIFO_SIZE];
struct semaphore sem;
wait_queue_head_t r_wait;
wait_queue_head_t w_wait;
struct fasync_struct *async_queue;
};
struct globalfifo_dev *globalfifo_devp;
int globalfifo_open(struct inode *inode, struct file *filp)
{
filp->private_data = globalfifo_devp;
return 0;
}
int globalfifo_release(struct inode *inode, struct file *filp)
{
globalfifo_fasync( - 1, filp, 0);
return 0;
}
static int globalfifo_ioctl(struct inode *inodep, struct file *filp, unsigned
int cmd, unsigned long arg)
{
struct globalfifo_dev *dev = filp->private_data;
switch (cmd)
{
case FIFO_CLEAR:
down(&dev->sem); //获得信号量
dev->current_len = 0;
memset(dev->mem,0,GLOBALFIFO_SIZE);
up(&dev->sem); //释放信号量
printk(KERN_INFO "globalfifo is set to zero/n");
break;
default:
return - EINVAL;
}
return 0;
}
static unsigned int globalfifo_poll(struct file *filp, poll_table *wait)
{
unsigned int mask = 0;
struct globalfifo_dev *dev = filp->private_data;
down(&dev->sem);
poll_wait(filp, &dev->r_wait, wait);
poll_wait(filp, &dev->w_wait, wait);
if (dev->current_len != 0)
{
mask |= POLLIN | POLLRDNORM;
}
if (dev->current_len != GLOBALFIFO_SIZE)
{
mask |= POLLOUT | POLLWRNORM;
}
up(&dev->sem);
return mask;
}
static int globalfifo_fasync(int fd, struct file *filp, int mode)
{
struct globalfifo_dev *dev = filp->private_data;
return fasync_helper(fd, filp, mode, &dev->async_queue);
}
static ssize_t globalfifo_read(struct file *filp, char __user *buf, size_t count,
loff_t *ppos)
{
int ret;
struct globalfifo_dev *dev = filp->private_data; //获得设备结构体指针
DECLARE_WAITQUEUE(wait, current); //定义等待队列
down(&dev->sem); //获得信号量
add_wait_queue(&dev->r_wait, &wait); //进入读等待队列头
if (dev->current_len == 0)
{
if (filp->f_flags &O_NONBLOCK)
{
ret = - EAGAIN;
goto out;
}
__set_current_state(TASK_INTERRUPTIBLE); //改变进程状态为睡眠
up(&dev->sem);
schedule(); //调度其他进程执行
if (signal_pending(current))
//如果是因为信号唤醒
{
ret = - ERESTARTSYS;
goto out2;
}
down(&dev->sem);
}
if (count > dev->current_len)
count = dev->current_len;
if (copy_to_user(buf, dev->mem, count))
{
ret = - EFAULT;
goto out;
}
else
{
memcpy(dev->mem, dev->mem + count, dev->current_len - count); //fifo数据前移
dev->current_len -= count; //有效数据长度减少
printk(KERN_INFO "read %d bytes(s),current_len:%d/n", count, dev->current_len);
wake_up_interruptible(&dev->w_wait); //唤醒写等待队列
ret = count;
}
out: up(&dev->sem); //释放信号量
out2:remove_wait_queue(&dev->w_wait, &wait); //从附属的等待队列头移除
set_current_state(TASK_RUNNING);
return ret;
}
static ssize_t globalfifo_write(struct file *filp, const char __user *buf,
size_t count, loff_t *ppos)
{
struct globalfifo_dev *dev = filp->private_data; //获得设备结构体指针
int ret;
DECLARE_WAITQUEUE(wait, current); //定义等待队列
down(&dev->sem); //获取信号量
add_wait_queue(&dev->w_wait, &wait); //进入写等待队列头
if (dev->current_len == GLOBALFIFO_SIZE)
{
if (filp->f_flags &O_NONBLOCK)
//如果是非阻塞访问
{
ret = - EAGAIN;
goto out;
}
__set_current_state(TASK_INTERRUPTIBLE); //改变进程状态为睡眠
up(&dev->sem);
schedule(); //调度其他进程执行
if (signal_pending(current))
//如果是因为信号唤醒
{
ret = - ERESTARTSYS;
goto out2;
}
down(&dev->sem); //获得信号量
}
if (count > GLOBALFIFO_SIZE - dev->current_len)
count = GLOBALFIFO_SIZE - dev->current_len;
if (copy_from_user(dev->mem + dev->current_len, buf, count))
{
ret = - EFAULT;
goto out;
}
else
{
dev->current_len += count;
printk(KERN_INFO "written %d bytes(s),current_len:%d/n", count, dev
->current_len);
wake_up_interruptible(&dev->r_wait); //唤醒读等待队列
if (dev->async_queue)
kill_fasync(&dev->async_queue, SIGIO, POLL_IN);
ret = count;
}
out: up(&dev->sem); //释放信号量
out2:remove_wait_queue(&dev->w_wait, &wait); //从附属的等待队列头移除
set_current_state(TASK_RUNNING);
return ret;
}
static const struct file_operations globalfifo_fops =
{
.owner = THIS_MODULE,
.read = globalfifo_read,
.write = globalfifo_write,
.ioctl = globalfifo_ioctl,
.poll = globalfifo_poll,
.open = globalfifo_open,
.release = globalfifo_release,
.fasync = globalfifo_fasync,
};
static void globalfifo_setup_cdev(struct globalfifo_dev *dev, int index)
{
int err, devno = MKDEV(globalfifo_major, index);
cdev_init(&dev->cdev, &globalfifo_fops);
dev->cdev.owner = THIS_MODULE;
dev->cdev.ops = &globalfifo_fops;
err = cdev_add(&dev->cdev, devno, 1);
if (err)
printk(KERN_NOTICE "Error %d adding LED%d", err, index);
}
int globalfifo_init(void)
{
int ret;
dev_t devno = MKDEV(globalfifo_major, 0);
if (globalfifo_major)
ret = register_chrdev_region(devno, 1, "globalfifo");
else
{
ret = alloc_chrdev_region(&devno, 0, 1, "globalfifo");
globalfifo_major = MAJOR(devno);
}
if (ret < 0)
return ret;
globalfifo_devp = kmalloc(sizeof(struct globalfifo_dev), GFP_KERNEL);
if (!globalfifo_devp)
{
ret = - ENOMEM;
goto fail_malloc;
}
memset(globalfifo_devp, 0, sizeof(struct globalfifo_dev));
globalfifo_setup_cdev(globalfifo_devp, 0);
init_MUTEX(&globalfifo_devp->sem);
init_waitqueue_head(&globalfifo_devp->r_wait);
init_waitqueue_head(&globalfifo_devp->w_wait);
return 0;
fail_malloc: unregister_chrdev_region(devno, 1);
return ret;
}
void globalfifo_exit(void)
{
cdev_del(&globalfifo_devp->cdev);
kfree(globalfifo_devp);
unregister_chrdev_region(MKDEV(globalfifo_major, 0), 1);
}
MODULE_AUTHOR("Song Baohua");
MODULE_LICENSE("Dual BSD/GPL");
module_param(globalfifo_major, int, S_IRUGO);
module_init(globalfifo_init);
module_exit(globalfifo_exit);
应用：
#include <sys/types.h>
#include <sys/stat.h>
#include <stdio.h>
#include <fcntl.h>
#include <signal.h>
#include <unistd.h>
void input_handler(int signum)
{
printf("receive a signal from globalfifo,signalnum:%d/n",signum);
}
main()
{
int fd, oflags;
fd = open("/dev/globalfifo", O_RDWR, S_IRUSR | S_IWUSR);
if (fd != - 1)
{
//启动信号驱动机制
signal(SIGIO, input_handler); //让input_handler()处理SIGIO信号
fcntl(fd, F_SETOWN, getpid());
oflags = fcntl(fd, F_GETFL);
fcntl(fd, F_SETFL, oflags | FASYNC);
while(1)
{
sleep(100);
}
}
else
{
printf("device open failure/n");
}
}
在板子上测试：
$ insmod globalfifo_async.ko
$ cat /proc/devices
Character devices:
1 mem
2 pty
3 ttyp
4 /dev/vc/0
4 tty
5 /dev/tty
5 /dev/console
5 /dev/ptmx
7 vcs
10 misc
13 input
14 sound
29 fb
81 video4linux
89 i2c
90 mtd
128 ptm
136 pts
180 usb
188 ttyUSB
204 s3c2410_serial
253 globalfifo
Block devices:
$ mknod /dev/globalfifo c 253 1
$ ./asyncmonitor &
执行本人门4中的read, write进程，结果如下
$ ./read &
/ $
********************
user read devices:
/ $ ./write &
/ $
user write devices:
written 1024 bytes(s),current_len:1024
receive a signal from globalfiread 1024 bytes(s),current_len:0
written 1024 bytes(s),current_len:1024
written 1024 bytes(s),current_len:2048
written 1024 bytes(s),current_len:3072
written 1024 bytes(s),current_len:4096
fo,signalnum:29
read count= :1024
write count is: 1024
user write devices:
receive a signal from globalfifo,signalnum:29
write count is: 1024
user write devices:
receive a signal from globalfifo,signalnum:29
write count is: 1024
user write devices:
receive a signal from globalfifo,signalnum:29
write count is: 1024
user write devices:
receive a signal from globalfifo,signalnum:29
write count is: 1024
user write devices:
********************
read 2048 bytes(s),current_len:2048
written 1024 bytes(s),current_len:3072
written 1024 bytes(s),current_len:4096
user read devices:
read count= :2048
write count is: 1024
user write devices:
receive a signal from globalfifo,signalnum:29
write count is: 1024
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