linux字符设备驱动之字符之异步通知

在前面的博文中记录的都是应用层主动查询读取驱动按键状态。驱动可不可以在有信号之后，主动上报通知应用层事件呢？当然可以，linux如此博大精深。我们使用异步通信机制，signal的办法实现该功能。

所谓的异步，就是进程可以在信号没到前干别的事情，等到信号到来了，进程就会被内核通知去做相应的信号操作。进程是不知道信号什么时候来的。

First of all,我们学习一下，应用层是怎样使用signal的。不叨叨，先贴代码。(show me the fucking code)

我们使用kill 信号编号值 PID 号来传递命令给这个应用程序。使用ps查看这个程序的PID号。

目标：按下按键时，驱动通知应用层程序

1：应用程序注册信号处理函数

2：驱动来主动发出信号

3：发给应用层

4：使用kill_fasync函数发出信号

那么我们的驱动程序跟应用程序该怎么写呢？show me the fucking code:

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/delay.h>
#include <linux/irq.h>
#include <asm/uaccess.h>
#include <asm/irq.h>
#include <asm/io.h>
#include <asm/arch/regs-gpio.h>
#include <asm/hardware.h>
#include <linux/poll.h>static struct class *fifthdrv_class;
static struct class_device	*fifthdrv_class_dev;volatile unsigned long *gpfcon;
volatile unsigned long *gpfdat;volatile unsigned long *gpgcon;
volatile unsigned long *gpgdat;static DECLARE_WAIT_QUEUE_HEAD(button_waitq);/* 中断事件标志, 中断服务程序将它置1，fifth_drv_read将它清0 */
static volatile int ev_press = 0;static struct fasync_struct *button_async;struct pin_desc{unsigned int pin;unsigned int key_val;
};/* 键值: 按下时, 0x01, 0x02, 0x03, 0x04 */
/* 键值: 松开时, 0x81, 0x82, 0x83, 0x84 */
static unsigned char key_val;struct pin_desc pins_desc[4] = {{S3C2410_GPF0, 0x01},{S3C2410_GPF2, 0x02},{S3C2410_GPG3, 0x03},{S3C2410_GPG11, 0x04},
};/** 确定按键值*/
static irqreturn_t buttons_irq(int irq, void *dev_id)
{struct pin_desc * pindesc = (struct pin_desc *)dev_id;unsigned int pinval;pinval = s3c2410_gpio_getpin(pindesc->pin);if (pinval){/* 松开 */key_val = 0x80 | pindesc->key_val;}else{/* 按下 */key_val = pindesc->key_val;}ev_press = 1;                  /* 表示中断发生了 */wake_up_interruptible(&button_waitq);   /* 唤醒休眠的进程 */kill_fasync (&button_async, SIGIO, POLL_IN);return IRQ_RETVAL(IRQ_HANDLED);
}static int fifth_drv_open(struct inode *inode, struct file *file)
{/* 配置GPF0,2为输入引脚 *//* 配置GPG3,11为输入引脚 */request_irq(IRQ_EINT0,  buttons_irq, IRQT_BOTHEDGE, "S2", &pins_desc[0]);request_irq(IRQ_EINT2,  buttons_irq, IRQT_BOTHEDGE, "S3", &pins_desc[1]);request_irq(IRQ_EINT11, buttons_irq, IRQT_BOTHEDGE, "S4", &pins_desc[2]);request_irq(IRQ_EINT19, buttons_irq, IRQT_BOTHEDGE, "S5", &pins_desc[3]);	return 0;
}ssize_t fifth_drv_read(struct file *file, char __user *buf, size_t size, loff_t *ppos)
{if (size != 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, 返回键值 */copy_to_user(buf, &key_val, 1);ev_press = 0;return 1;
}int fifth_drv_close(struct inode *inode, struct file *file)
{free_irq(IRQ_EINT0, &pins_desc[0]);free_irq(IRQ_EINT2, &pins_desc[1]);free_irq(IRQ_EINT11, &pins_desc[2]);free_irq(IRQ_EINT19, &pins_desc[3]);

fifth_drv_fasync (-1,filp,0);

return 0;}static unsigned fifth_drv_poll(struct file *file, poll_table *wait){unsigned int mask = 0;poll_wait(file, &button_waitq, wait); // 不会立即休眠if (ev_press)mask |= POLLIN | POLLRDNORM;return mask;}static int fifth_drv_fasync (int fd, struct file *filp, int on){printk("driver: fifth_drv_fasync\n");return fasync_helper (fd, filp, on, &button_async);}static struct file_operations sencod_drv_fops = { .owner = THIS_MODULE, /* 这是一个宏，推向编译模块时自动创建的__this_module变量 */ .open = fifth_drv_open, .read = fifth_drv_read, .release = fifth_drv_close,.poll = fifth_drv_poll,.fasync = fifth_drv_fasync,};int major;static int fifth_drv_init(void){major = register_chrdev(0, "fifth_drv", &sencod_drv_fops);fifthdrv_class = class_create(THIS_MODULE, "fifth_drv");fifthdrv_class_dev = class_device_create(fifthdrv_class, NULL, MKDEV(major, 0), NULL, "buttons"); /* /dev/buttons */gpfcon = (volatile unsigned long *)ioremap(0x56000050, 16);gpfdat = gpfcon + 1;gpgcon = (volatile unsigned long *)ioremap(0x56000060, 16);gpgdat = gpgcon + 1;return 0;}static void fifth_drv_exit(void){unregister_chrdev(major, "fifth_drv");class_device_unregister(fifthdrv_class_dev);class_destroy(fifthdrv_class);iounmap(gpfcon);iounmap(gpgcon);return 0;}module_init(fifth_drv_init);module_exit(fifth_drv_exit);MODULE_LICENSE("GPL");

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#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>/* sixthdrvtest */
int fd;void my_signal_fun(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;int Oflags;//signal(SIGIO, my_signal_fun);fd = open("/dev/buttons", O_RDWR | O_NONBLOCK);if (fd < 0){printf("can't open!\n");return -1;}fcntl(fd, F_SETOWN, getpid());Oflags = fcntl(fd, F_GETFL); fcntl(fd, F_SETFL, Oflags | FASYNC);while (1){sleep(1000);}return 0;
}