韦东山驱动视频笔记——4.字符设备驱动程序之异步通知

linux内核版本：linux-2.6.30.4

目的：我们前面写的几个驱动程序不管是查询方式、中断方式还是poll方式，都要求我们应用程序去主动的查询，看有没有按键发生，要想实现不需要让应用程序主动去查询，而是按键产生后，由驱动主动告诉应用，就要实现异步通知方式。

为了使设备支持异步通知机制，驱动程序中涉及以下3项工作：

1.支持F_SETOWN命令，能在这个控制命令处理中设置file->f_owner为对应进程ID，不过此项工作已由内核完成，设备驱动无须处理

2.支持F_SETFL命令的处理，每当FASYNC标志改变时，驱动程序中的fasync()函数将得以执行，驱动中应该实现fasync()函数

3.在设备资源可获得时，调用kill_fasync()函数激发相应的信号

#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 <linux/device.h>
#include <linux/irq.h>
#include <linux/interrupt.h>
#include <mach/regs-gpio.h>
#include <linux/poll.h>

static struct class *fifth_drv_class;
static struct class_device  *fifth_drv_class_dev;

static volatile unsigned long *gpfcon;
static volatile unsigned long *gpfdat;
static int major;

struct pin_desc
{
unsigned int pin;
unsigned int key_val;
};

static unsigned char key_val;

static struct pin_desc pins_desc[4] =
{
{S3C2410_GPF1, 0x01},
{S3C2410_GPF4, 0x02},
{S3C2410_GPF2, 0x03},
{S3C2410_GPF0, 0x04},
};

static DECLARE_WAIT_QUEUE_HEAD(button_waitq);
static volatile int ev_press = 0;
static struct fasync_struct *button_async;

static irqreturn_t buttons_irq(int irq, void *dev_id)
{
struct pin_desc *pin = (struct pin_desc *)dev_id;
unsigned int pinval;
pinval = s3c2410_gpio_getpin(pin->pin);

if (pinval)
{
//松开
key_val = 0x80 | pin->key_val;
}
else
{
//按下
key_val = pin->key_val;
}

wake_up_interruptible(&button_waitq);
ev_press = 1;
kill_fasync(&button_async, SIGIO, POLL_IN);

return IRQ_HANDLED;
}

static int fifth_drv_open(struct inode *inode, struct file *file)
{
request_irq(IRQ_EINT1, buttons_irq, IRQ_TYPE_EDGE_BOTH, "S1", &pins_desc[0]);
request_irq(IRQ_EINT4, buttons_irq, IRQ_TYPE_EDGE_BOTH, "S2", &pins_desc[1]);
request_irq(IRQ_EINT2, buttons_irq, IRQ_TYPE_EDGE_BOTH, "S3", &pins_desc[2]);
request_irq(IRQ_EINT0, buttons_irq, IRQ_TYPE_EDGE_BOTH, "S4", &pins_desc[3]);
return 0;
}

static ssize_t fifth_drv_read(struct file *file, char __user *buf,
size_t count, loff_t *ppos)
{
if (count != 1)
return -EINVAL;
/*如果没有按键动作，休眠*/
wait_event_interruptible(button_waitq, ev_press);

/*如果有按键动作发生，返回键值*/
copy_to_user(buf, &key_val, 1);
ev_press = 0;
return 1;
}

static int fifth_drv_release(struct inode *inode, struct file *file)
{
free_irq(IRQ_EINT1, &pins_desc[0]);
free_irq(IRQ_EINT4, &pins_desc[1]);
free_irq(IRQ_EINT2, &pins_desc[2]);
free_irq(IRQ_EINT0, &pins_desc[3]);
return 0;
}

static unsigned int fifth_drv_poll(struct file *file, poll_table *wait)

{
unsigned int mask = 0;

/*这并不会休眠，只是把当前进程挂到队列里*/
poll_wait(file, &button_waitq, wait);

if (ev_press)
{
mask |= (POLLIN | POLLRDNORM);
}
return mask;
}

static int fifth_drv_fasync(int fd, struct file *file, int on)
{
printk("driver:fifth_drv_fasync\n");
return fasync_helper(fd, file, on, &button_async);
}

static struct file_operations fifth_fops = {
.owner = THIS_MODULE,
.open = fifth_drv_open,
.read = fifth_drv_read,
.poll = fifth_drv_poll,
.fasync = fifth_drv_fasync,
.release  = fifth_drv_release,
};

int fifth_init()
{
int ret;
major = register_chrdev(0, "fifth_drv", &fifth_fops);
fifth_drv_class = class_create(THIS_MODULE, "fifth_drv");
device_create(fifth_drv_class, NULL, MKDEV(major, 0), NULL, "buttons");

gpfcon = (volatile unsigned long *)ioremap(0x56000050, 16);
gpfdat = gpfcon + 1;

return 0;
}
static void fifth_exit()
{
unregister_chrdev(major, "fifth_drv");
device_destroy(fifth_drv_class, MKDEV(major, 0));
class_destroy(fifth_drv_class);
iounmap(gpfcon);
}

module_init(fifth_init);
module_exit(fifth_exit);

MODULE_LICENSE("GPL");

测试程序：

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

/* fifthdrvtest
*/

int fd;

void my_signal_func(int signum)
{
unsigned char key_val;
read(fd, &key_val, 1);
printf("key_val ===0x%x\n", key_val);
}
int main(int argc, char **argv)
{
unsigned char key_val;
int ret, oflags;

signal(SIGIO, my_signal_func);

fd = open("/dev/buttons", O_RDWR);
if (fd < 0)
{
printf("can't open!\n");
}

fcntl(fd, F_SETOWN, getpid());
oflags = fcntl(fd, F_GETFL);
fcntl(fd, F_SETFL, oflags|FASYNC);
while (1)
{
sleep(1000);
}

return 0;
}

运行效果：