字符设备驱动之同步-信号

#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include




static struct class *sixthdrv_class;
static struct class_device *sixthdrv_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，sixth_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},
};


//static atomic_t canopen = ATOMIC_INIT(1);     //定义原子变量并初始化为1


static DECLARE_MUTEX(button_lock);     //定义互斥锁


/*
  * 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 sixth_drv_open(struct inode *inode, struct file *file)
{

/* 获取信号量 */
down(&button_lock);



/* 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 sixth_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 sixth_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]);
up(&button_lock);
return 0;
}


static unsigned sixth_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 sixth_drv_fasync (int fd, struct file *filp, int on)
{
printk("driver: sixth_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    =  sixth_drv_open,     
.read = sixth_drv_read,   
.release =  sixth_drv_close,
.poll    =  sixth_drv_poll,
.fasync =  sixth_drv_fasync,
};




int major;
static int sixth_drv_init(void)
{
major = register_chrdev(0, "sixth_drv", &sencod_drv_fops);


sixthdrv_class = class_create(THIS_MODULE, "sixth_drv");


sixthdrv_class_dev = class_device_create(sixthdrv_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 sixth_drv_exit(void)
{
unregister_chrdev(major, "sixth_drv");
class_device_unregister(sixthdrv_class_dev);
class_destroy(sixthdrv_class);
iounmap(gpfcon);
iounmap(gpgcon);
return 0;
}




module_init(sixth_drv_init);


module_exit(sixth_drv_exit);


MODULE_LICENSE("GPL");

测试程序
#include
#include
#include
#include
#include
#include
#include
#include
#include

/* 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)
{
ret = read(fd, &key_val, 1);
printf("key_val: 0x%x, ret = %d\n", key_val, ret);
sleep(5);
}

return 0;
}
2. 信号量
信号量（semaphore）是用于保护临界区的一种常用方法，只有得到信号量的进程才能执行临界区代码。
当获取不到信号量时，进程进入休眠等待状态。

定义信号量
struct semaphore sem;
初始化信号量
void sema_init (struct semaphore *sem, int val);
void init_MUTEX(struct semaphore *sem);//初始化为0

static DECLARE_MUTEX(button_lock);     //定义互斥锁

获得信号量
void down(struct semaphore * sem);
int down_interruptible(struct semaphore * sem); 
int down_trylock(struct semaphore * sem);
释放信号量
void up(struct semaphore * sem);