Pmode VGA switch help

[srg_13]

Hi!
I've got this (C) code to change to 320x200 graphics mode form pmode (attached). The problem is that it uses two ASM commands that I have not yet implemented: outpw and outp.

I have code for outb from the osfaq, and if I changed the outb to outw or outpw, would that work?

Thanks,

Stephen

[Warrior]

Outpw afaik writes a word to the given port

outp afaik writes a byte to the given port

Same with in*

[srg_13]

I have this code:

Code: Select all

static __inline__ void outb(unsigned short port, unsigned char val)
{
   asm volatile("outb %0,%1"::"a"(val), "Nd" (port));
}

If I change it to

Code: Select all

static __inline__ void outp(unsigned short port, unsigned char val)
{
   asm volatile("outp %0,%1"::"a"(val), "Nd" (port));
}

will that work?
Also, will it work with outpw?

Thanks,

Stephen

[durand]

From my experience, an out with a "p" indicates that a pause is present after the IO operation.

So you get the straight ones: outb, outw
And the ones with pauses: outpb, outpw

[Pype.Clicker]

the 'pause' thing is something that is introduced by programmers. There's no such thing like "outp*" in the instruction set...

[srg_13]

So how would you implement them? Do you have any code samples?

Stephen

[Brendan]

Hi,

So how would you implement them? Do you have any code samples?

I'd implement them with something like this:

Code: Select all

    out dx,al
    jmp .l1
.l1:
   jmp .l2
.l2:

But some people read from a dummy IO port instead..

To be honest, I wouldn't actually implement them at all - they aren't needed on 80486 or above computers....


Cheers,

Brendan