字符设备驱动之轮询

按键查询之轮询  
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include

static struct class *seconddrv_class;
static struct class_device *seconddrv_class_dev;
volatile unsigned long *gpfcon;
volatile unsigned long *gpfdat;
volatile unsigned long *gpgcon;
volatile unsigned long *gpgdat;


static int second_drv_open(struct inode *inode, struct file *file)
{
    /* 配置GPF0,2为输入引脚 */
    *gpfcon &= ~((0x3<<(0*2)) | (0x3<<(2*2)));
    /* 配置GPG3,11为输入引脚 */
    *gpgcon &= ~((0x3<<(3*2)) | (0x3<<(11*2)));
    return 0;
}


ssize_t second_drv_read(struct file *file, char __user *buf, size_t size, loff_t *ppos)
{
    /* 返回4个引脚的电平 */
    unsigned char key_vals[4];
    int regval;
    if (size != sizeof(key_vals))
    return -EINVAL;


    /* 读GPF0,2 */
    regval = *gpfdat;
    key_vals[0] = (regval & (1<<0)) ? 1 : 0;
    key_vals[1] = (regval & (1<<2)) ? 1 : 0;

    /* 读GPG3,11 */
    regval = *gpgdat;
    key_vals[2] = (regval & (1<<3)) ? 1 : 0;
    key_vals[3] = (regval & (1<<11)) ? 1 : 0;
    copy_to_user(buf, key_vals, sizeof(key_vals));
    return sizeof(key_vals);
}

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   =   second_drv_open,     
.read = second_drv_read,   
};

int major;
static int second_drv_init(void)
{
    major = register_chrdev(0, "second_drv", &sencod_drv_fops);
    seconddrv_class = class_create(THIS_MODULE, "second_drv");
    seconddrv_class_dev = class_device_create(seconddrv_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 second_drv_exit(void)
{
    unregister_chrdev(major, "second_drv");
    class_device_unregister(seconddrv_class_dev);
    lass_destroy(seconddrv_class);
    iounmap(gpfcon);
    iounmap(gpgcon);
    return 0;
}

module_init(second_drv_init);
module_exit(second_drv_exit);
MODULE_LICENSE("GPL");

测试程序
#include
#include
#include
#include
/* seconddrvtest 
  */
int main(int argc, char **argv)
{
    int fd;
    nsigned char key_vals[4];
    nt cnt = 0;

    fd = open("/dev/buttons", O_RDWR);
    if (fd < 0)
    {
        printf("can't open!\n");
    }
       while (1)
    {
        read(fd, key_vals, sizeof(key_vals));
        f (!key_vals[0] || !key_vals[1] || !key_vals[2] || !key_vals[3])
        {
                printf("%04d key pressed: %d %d %d %d\n", cnt++, key_vals[0], key_vals[1], key_vals[2], key_vals[3]);
        }
      }
        return 0;
}

1 .轮询cpu 占用很高