Sender: M DOT A DOT Bukin AT inp DOT nsk DOT su
To: djgpp AT delorie DOT com
Subject: Re: PLEASE HELP with ExtAsm
References: <66e3ui$9jd$1 AT duke DOT telepac DOT pt>
From: Michael Bukin <M DOT A DOT Bukin AT inp DOT nsk DOT su>
Date: 08 Dec 1997 15:17:10 +0600
In-Reply-To: "Hugo Jose Ferreira"'s message of Sun, 7 Dec 1997 12:17:32 -0500
Message-Id: <20ra7onqi1.fsf@Sky.inp.nsk.su>
Lines: 58
Precedence: bulk

"Hugo Jose Ferreira" <hugojf AT mail DOT telepac DOT pt> writes:

> Can someone, please, help me with this Assembly Routine...
> Please, Correct this function:
> 
> void setdaccolor(byte color, byte red, byte green, byte blue) {
> __asm__ __volatile__ (
>   "movw  $0x3C8, %%dx \n\t"
>   "outb  %%al, %%dx \n\t"
>   "movw  $0x3C9, %%dx \n\t"
>   "movb  red, %%al \n\t"
>   "outb  %%al, %%dx \n\t"
>   "movb  green, %%al \n\t"
>   "outb  %%al, %%dx \n\t"
>   "movb  blue, %%al \n\t"
>   "outb  %%al, %%dx"
>   : : "rm" (color)
>   : "%eax", "%edx" );
> }

I don't think your need any assembly here.

void setdaccolor (byte color, byte red, byte green, byte blue)
{
  outportb (0x3C8, color);
  outportb (0x3C9, red);
  outportb (0x3C9, green);
  outportb (0x3C9, blue);
}

Or (trying to add some "optimizations"):

void setdaccolor (byte color, byte red, byte green, byte blue)
{
  int port = 0x3C8;
  outportb (port++, color);
  outportb (port, red);
  outportb (port, green);
  outportb (port, blue);
}

But I don't think this will be any better (try both and choose best
one).

Compile it with: gcc -Wall -O2 -S setdac.c
And see the resulting code in setdac.s

Also, try the following commands:

info gcc invo
(for gcc switches)

info libc alpha outport
(for outport prototype, which headers to include...)

I have not tested the above functions because I have not DJGPP here,
but they should work (after inclusion of correct header and defining
`byte' type).