字符设备驱动程序之poll机制
驱动源码: unsigned int pin; unsigned int key_val; {S3C2410_GPF0, 0x01}, {S3C2410_GPF2, 0x02}, {S3C2410_GPG3, 0x03}, {S3C2410_GPG11, 0x04}, 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 return IRQ_RETVAL(IRQ_HANDLED); 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; if(size != sizeof(key_val)) 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; 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; unsigned int mask = 0; poll_wait(file, &button_waitq, wait); // 不会立即休眠 if (ev_press) mask |= POLLIN | POLLRDNORM; //有数据可读 return mask; .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 = key_drv_open, .read = key_drv_read, .release = key_drv_close, .poll = key_drv_poll, 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; unregister_chrdev(major, "key_drv"); class_device_unregister(keydrv_class_dev); class_destroy(keydrv_class); iounmap(gpfcon); iounmap(gpgcon); return 0; int fd; unsigned char key_vals; int ret; struct pollfd fds[1]; fd = open("/dev/buttons", O_RDWR); if(fd < 0) printf("cant open!n"); fds[0].fd = fd; fds[0].events = POLLIN; while(1) { ret = poll(fds, 1, 5000); //5000是毫秒为单位,等待5S钟判断fds[0].fd文件是否有新数据可读 if(ret == 0) { printf("time out !n"); //超时 } else { read(fd, &key_vals, 1); //有数据可读 printf("key_vals = 0x%xn", key_vals); } } return 0; key_drv_poll函数就去查询有没有按键值更新(/dev/buttons),如果按键按下则返回,否则休眠,等到休眠时间到则自动返回;
#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{
};
struct pin_desc pins_desc[4] = {
};
// 键值: 按下时, 0x01, 0x02, 0x03, 0x04
// 键值: 松开时, 0x81, 0x82, 0x83, 0x84
static unsigned char key_val;
static DECLARE_WAIT_QUEUE_HEAD(button_waitq);
// 中断事件标志, 中断服务程序将它置1,third_drv_read将它清0
static volatile int ev_press = 0;
static irqreturn_t buttons_irq(int irq, void *dev_id)
{
}
static int key_drv_open(struct inode *inode, struct file *file)
{
}
ssize_t key_drv_read(struct file *file, char __user *buf, size_t size, loff_t *ppos)
{
}
int key_drv_close(struct inode *inode, struct file *file)
{
}
static unsigned key_drv_poll(struct file *file, poll_table *wait)
{
}
static struct file_operations key_drv_fops = {
};
static int key_drv_init(void)
{
}
static void key_drv_exit(void)
{
}
module_init(key_drv_init);
module_exit(key_drv_exit);
MODULE_LICENSE("GPL");
=================================================================
测试源码:
#include
#include
#include
#include
#include
int main(int argc, char **argv)
{
}
==================================================================
解析:
1、key_drv_fops 结构体中增加:.poll = key_drv_poll,
2、应用程序中循环调用poll函数,判断按键值有没有更新;如果更新则读取,否则超时提醒。


关键词: 字符设备驱动程序poll机

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