Read/write IO ports on NT

Read/write IO ports on NT

[Clive Mayo]

Hi

Trying to read and write directly at IO port on NT, using the following code

int main()
{
 __asm("mov $1, %al");
 __asm("mov $0x3f8, %dx");
 __asm("out %al, %dx");
 return 0;
}

also tried

int main()
{
 _outp(0x378, 1);
 return 0;
}

but get the following exception, Privileged instruction.
Any suggestions or pointers of how to code this.

Clive Mayo


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Re: Read/write IO ports on NT

[Corinna Vinschen]

On Tue, Jul 24, 2001 at 11:15:40AM +0100, Clive Mayo wrote:
> Hi
> 
> Trying to read and write directly at IO port on NT, using the following code
> 
> int main()
> {
>  __asm("mov $1, %al");
>  __asm("mov $0x3f8, %dx");
>  __asm("out %al, %dx");
>  return 0;
> }
> 
> also tried
> 
> int main()
> {
>  _outp(0x378, 1);
>  return 0;
> }
> 
> but get the following exception, Privileged instruction.
> Any suggestions or pointers of how to code this.

You can't on NT. Use standard file IO.

Corinna

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Re: Read/write IO ports on NT

[Gunnar Andre Dalsnes]

At 24.07.01 12:15 , you wrote:
>Hi
>
>Trying to read and write directly at IO port on NT, using the following code
>
>int main()
>{
>  __asm("mov $1, %al");
>  __asm("mov $0x3f8, %dx");
>  __asm("out %al, %dx");
>  return 0;
>}
>
>also tried
>
>int main()
>{
>  _outp(0x378, 1);
>  return 0;
>}
>
>but get the following exception, Privileged instruction.
>Any suggestions or pointers of how to code this.
>
>Clive Mayo

You need a kernel-mode device driver to do this.
Get sample source from Dr. Dobb's Journal.
ftp://ftp.ddj.com/1996/1996.05/directio.zip

Gunnar.


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