linux驱动之异步通信

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]);    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");

———————————————————-我-是漂亮的分割线——————————————————————————————————————————
/* sixthdrvtest
*/
#include

#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>

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;

}