字符設備驅動程序之異步通知

驅動源碼：

#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"

int major = 0;

static struct class *keydrv_class;

static struct class_device *keydrv_class_dev;

volatile unsigned long *gpfcon;

volatile unsigned long *gpfdat;

volatile unsigned long *gpgcon;

volatile unsigned long *gpgdat;

struct pin_desc{

unsigned int pin;

unsigned int key_val;

};

struct pin_desc pins_desc[4] = {

{S3C2410_GPF0, 0x01},

{S3C2410_GPF2, 0x02},

{S3C2410_GPG3, 0x03},

{S3C2410_GPG11, 0x04},

};

// 鍵值: 按下時, 0x01, 0x02, 0x03, 0x04

// 鍵值: 松開時, 0x81, 0x82, 0x83, 0x84

static unsigned char key_val;

static DECLARE_WAIT_QUEUE_HEAD(button_waitq);

// 中斷事件標志, 中斷服務程序將它置1，third_drv_read將它清0

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 * pindesc = (struct pin_desc *)dev_id;

unsigned int pinval;

pinval = s3c2410_gpio_getpin(pindesc->pin);

if(pinval)

{

//松開

key_val = 0x80 | pindesc->key_val;

}

else

{

//按下

key_val = pindesc->key_val;

}

ev_press = 1; //表示中斷發生了

wake_up_interruptible(&button_waitq); // 喚醒休眠的進程

kill_fasync (&button_async, SIGIO, POLL_IN);

return IRQ_RETVAL(IRQ_HANDLED);

}

static int key_drv_open(struct inode *inode, struct file *file)

{

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 key_drv_read(struct file *file, char __user *buf, size_t size, loff_t *ppos)

{

if(size != sizeof(key_val))

return -EINVAL;

// 如果沒有按鍵動作, 休眠

wait_event_interruptible(button_waitq, ev_press);

// 如果有按鍵動作, 返回鍵值

copy_to_user(buf, &key_val, 1);

ev_press = 0;

return 1;

}

int key_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 key_drv_poll(struct file *file, poll_table *wait)

{

unsigned int mask = 0;

poll_wait(file, &button_waitq, wait); // 不會立即休眠

if (ev_press)

mask |= POLLIN | POLLRDNORM;

return mask;

}

static int key_drv_fasync (int fd, struct file *filp, int on)

{

printk("driver: fifth_drv_fasyncn");

return fasync_helper(fd, filp, on, &button_async);

}

static struct file_operations key_drv_fops = {

.owner = THIS_MODULE, // 這是一個宏，推向編譯模塊時自動創建的__this_module變量

.open = key_drv_open,

.read = key_drv_read,

.release = key_drv_close,

.poll = key_drv_poll,

.fasync = key_drv_fasync,

};

static int key_drv_init(void)

{

major = register_chrdev(0, "key_drv", &key_drv_fops);

keydrv_class = class_create(THIS_MODULE, "key_drv");

keydrv_class_dev = class_device_create(keydrv_class, NULL, MKDEV(major, 0), NULL, "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 key_drv_exit(void)

{

unregister_chrdev(major, "key_drv");

class_device_unregister(keydrv_class_dev);

class_destroy(keydrv_class);

iounmap(gpfcon);

iounmap(gpgcon);

return 0;

}

module_init(key_drv_init);

module_exit(key_drv_exit);

MODULE_LICENSE("GPL");

=====================================================================

測試程序：

#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"

int fd;

void my_signal_fun(int signum)

{

unsigned char key_val;

read(fd, &key_val, 1);

printf("key_val: 0x%xn", key_val);

}

int main(int argc, char **argv)

{

int Oflags;

signal(SIGIO, my_signal_fun);

fd = open("/dev/buttons", O_RDWR);

if(fd < 0)

printf("cant open!n");

fcntl(fd, F_SETOWN, getpid());

Oflags = fcntl(fd, F_GETFL);

fcntl(fd, F_SETFL, Oflags | FASYNC);

while(1)

{

sleep(1000);

}

return 0;

}

===================================================================

解析：

1、驅動程序中定義static struct fasync_struct *button_async;

在key_drv_fops結構體中增加 .fasync = key_drv_fasync,

在key_drv_fasync 函數中初始化變量button_async；

在中斷處理函數中發送信號：kill_fasync (&button_async, SIGIO, POLL_IN);

2、測試程序中定義信號接收函數：signal(SIGIO, my_signal_fun);

初始化，告訴驅動程序信號發給誰（進程PID）：

fcntl(fd, F_SETOWN, getpid());

Oflags = fcntl(fd, F_GETFL);

fcntl(fd, F_SETFL, Oflags | FASYNC);

總結：正常情況下進程休眠，當有按鍵按下后驅動程序中的按鍵中斷處理函數就會發送信號給休眠的應用程序，應用程序接收到信號以后進入處理函數讀取按鍵值。