static void touch_timer_fire(unsigned long data)
{
      unsigned long data0;
      unsigned long data1;
    int updown;

      data0 = ioread32(base_addr+S3C2410_ADCDAT0);
      data1 = ioread32(base_addr+S3C2410_ADCDAT1);

     updown = (!(data0 & S3C2410_ADCDAT0_UPDOWN)) && (!(data1 & S3C2410_ADCDAT0_UPDOWN));

     if (updown) {
         if (count != 0) {
            long tmp;
                                                                                                
            tmp = xp;
            xp = yp;
            yp = tmp;
                                                                                                
                        xp >>= 2;
                        yp >>= 2;            
input_report_abs(dev, ABS_X, xp);
             input_report_abs(dev, ABS_Y, yp);

             input_report_key(dev, BTN_TOUCH, 1);
             input_report_abs(dev, ABS_PRESSURE, 1);
             input_sync(dev);
         }

         xp = 0;
         yp = 0;
         count = 0;

         iowrite32(S3C2410_ADCTSC_PULL_UP_DISABLE | AUTOPST, base_addr+S3C2410_ADCTSC);
         iowrite32(ioread32(base_addr+S3C2410_ADCCON) | S3C2410_ADCCON_ENABLE_START, base_addr+S3C2410_ADCCON);
     } else {
         count = 0;

         input_report_key(dev, BTN_TOUCH, 0);
         input_report_abs(dev, ABS_PRESSURE, 0);
         input_sync(dev);

         iowrite32(WAIT4INT(0), base_addr+S3C2410_ADCTSC);
        if (OwnADC) {
            OwnADC = 0;
            up(&ADC_LOCK);
        }
     }
}


请问下红色标注的地方在驱动中起什么作用，为什么要交换变量，为什么要移动2位

没有人回答吗自己顶一下

代码不完整，猜测是采样4次所以要除以4求平均值

是的，确实是取了4次的值之后，嗯你这么说我就有点理解了，但是为什么要经过变量传递呢，也就是为什么要将xp与yp的值互换呢