字符设备驱动笔记——异步通知（八）

一、信号处理函数的要点：
1.注册一个信号处理函数
2.发信号，谁发
3.发给谁
4.怎么发

#include <stdio.h>
#include <signal.h>

void my_signal_fun(int signum)
{
    static int cnt = 0;
    printf("signal = %d, %d times
", signum, ++cnt);
}

int main(int argc, char **argv)
{

    signal(SIGUSR1, my_signal_fun);
    
    while (1)
    {
        sleep(1000);
    }
    return 0;
}

二、执行：

//执行 kill -USR1 833
//或者
//kill -10 833
//kill -9 833

三、驱动程序
目标：
按下按键时，驱动程序通知应用程序
步骤：
1.应用程序中注册信号处理函数
2.驱动程序发送信号
3.信号发给应用程序，应用程序告诉驱动程序PID
4.驱动程序：kill_fasync

实现：

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filp->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


应用程序：
应用程序调用fcntl()函数告诉驱动程序，发给谁
fcntl(fd, F_SETOWN, getpid());  // 告诉内核，发给谁

//修改flag
Oflags = fcntl(fd, F_GETFL);   
fcntl(fd, F_SETFL, Oflags | FASYNC);  // 改变fasync标记，最终会调用到驱动的faync > fasync_helper：初始化/释

放fasync_struct

四、fifth_drv.c

#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
");
    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");

五、fifthdrvtest.c

#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_fun(int signum)
{
    unsigned char key_val;
    read(fd, &key_val, 1);
    printf("key_val: 0x%x
", 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);
    if (fd < 0)
    {
        printf("can't open!
");
    }

    fcntl(fd, F_SETOWN, getpid());
    
    Oflags = fcntl(fd, F_GETFL); 
    
    fcntl(fd, F_SETFL, Oflags | FASYNC);


    while (1)
    {
        sleep(1000);
    }
    
    return 0;
}

六、Makefile

KERN_DIR = /work/system/linux-2.6.22.6

all:
    make -C $(KERN_DIR) M=`pwd` modules 

clean:
    make -C $(KERN_DIR) M=`pwd` modules clean
    rm -rf modules.order

obj-m    += fifth_drv.o