The HyperNews Linux KHG Discussion Pages

## How to invalidate a chache page

  Forum: The Linux Kernel Hackers' Guide
  Keywords: Chache Problem
  Date: Wed, 21 May 1997 17:47:36 GMT
  From: Gerhard Uttenthaler <u7x62bt@sun1.lrz-muenchen.de>

Hello everybody, I have a problem with a char device driver, which I think is related to a chaching problem. In my interrupt routine where I receive data from my device I have to handle a specific protocol depending on my device. So I have to poll a specific address until a change at this address occurs. Something like this:
    do{
      status = readb(0xc0000);
       timeout++;
    }while(!(status & 0x80) && (timeout < 2000));
Sometimes I get timeouts, which can only occur if I read chache memory which is not up to date. The device is fast and works pretty well under DOS and Win311. The situation is quite similiar on write access, where I must be sure to write directly to the device, not into the chache waiting for a flush. The question is: Does anyone know how to invalidate the chache on my address or how to tell the chache not to chache my device at all??? Thank you very much! G. Uttenthaler u7x62bt@sun1.lrz-muenchen.de

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1. Read the rest of the KHG! by Michael K. Johnson