Linux驱动之poll机制
上篇文章的链接：http://blog.csdn.net/qq_21792169/article/details/48415987
驱动程序：
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
/*
* 休眠用的队列的一个宏
*/
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;
#define DEVICE_NAME "poll"
static struct class *poll_class;
struct pin_desc{
unsigned int pin;
unsigned int key_val;
};
static unsigned char keyval;//jianzhi
/* 键值: 按下时, 0x01, 0x02, 0x03, 0x04 */
/* 键值: 松开时, 0x81, 0x82, 0x83, 0x84 */
struct pin_desc pins_desc[4] = {
{S3C2410_GPF0, 0x01},
{S3C2410_GPF2, 0x02},
{S3C2410_GPF3, 0x03},
{S3C2410_GPF4, 0x04},
};
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); /* 获取当前案件之 */
if (pinval)
{
/* 松开 */
keyval = 0x80 | pindesc->key_val;
}
else
{
/* 按下 */
keyval = 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 */
return IRQ_HANDLED;
}
static int fifth_drv_open(struct inode *inode, struct file *file) /* 应用程序调用open时候就调用这里，这时候在注册中断函数 */
{
request_irq(IRQ_EINT0, buttons_irq, IRQF_TRIGGER_FALLING|IRQF_TRIGGER_RISING, "S2", &pins_desc[0]);
request_irq(IRQ_EINT2, buttons_irq, IRQF_TRIGGER_FALLING|IRQF_TRIGGER_RISING, "S3", &pins_desc[1]);
request_irq(IRQ_EINT3, buttons_irq, IRQF_TRIGGER_FALLING|IRQF_TRIGGER_RISING, "S4", &pins_desc[2]);
request_irq(IRQ_EINT4, buttons_irq, IRQF_TRIGGER_FALLING|IRQF_TRIGGER_RISING, "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);//可以删除为了增加稳定
/* 如果有按键动作, 返回键值 */
copy_to_user(buf, &keyval, 1);
ev_press = 0;//继续休眠
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
//当中段发生时候要用wake_up_interruptible(&button_waitq);才会退出
if (ev_press)
mask |= POLLIN | POLLRDNORM;
return mask;//
}
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_EINT3, &pins_desc[2]);
free_irq(IRQ_EINT4, &pins_desc[3]);
return 0;
}
static struct file_operations fifth_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,
};
static int major; /* 自动分配主设备号 */
static int fifth_drv_init(void)
{
major = register_chrdev(0, DEVICE_NAME, &fifth_drv_fops); /* 注册这个fifth_drv_fops结构体 */
poll_class = class_create(THIS_MODULE, DEVICE_NAME); /* 创建类 */
device_create(poll_class, NULL, MKDEV(major, 0), NULL, "poll"); /* 类下面创建设备节点，这里利用了mdev机制自动创建设备节点 */
return 0;
}
static void fifth_drv_exit(void)
{
unregister_chrdev(major, "poll"); /* 卸载 */
device_destroy(poll_class,MKDEV(major, 0)); /* 删除类下面的设备节点 */
class_destroy(poll_class); /* 删除类 */
}
module_init(fifth_drv_init); /* 入口函数 */
module_exit(fifth_drv_exit);
MODULE_LICENSE("GPL"); /* 协议 */
测试程序：
#include
#include
#include
#include
#include
int main(int argc, char **argv)
{
int fd;
unsigned char key_val;
int ret;
struct pollfd fds[1];
fd = open("/dev/poll", O_RDWR);
if (fd < 0)
{
printf("can't open!\n");
}
fds[0].fd = fd;
fds[0].events = POLLIN;
while (1)
{
ret = poll(fds, 1, 5000);
if (ret == 0)
{
printf("time out\n");
}
else
{
read(fd, &key_val, 1);
printf("key_val = 0x%x\n", key_val);
}
}
return 0;
}
Makefile其他的部分是不变的，只需要修改文件名字就可以了。
obj-m :=pollt.o
KERNELDIR ?= /home/work/Linux/linux-2.6.28.7
PWD := $(shell pwd)
default:
$(MAKE) -C $(KERNELDIR) M=$(PWD) modules
clean:
rm -f *o *.mod.o *mod.c *.symvers *.order