From mboxrd@z Thu Jan  1 00:00:00 1970
From: Brian Gerst <brgerst@gmail.com>
Subject: Re: How to move two valuables to x86 CPU register ebx, ecx by using 
	AT&A inline asm.
Date: Mon, 23 Nov 2009 00:43:47 -0500
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To: Johnny Hung <johnny.hacking@gmail.com>
Cc: Jiri Slaby <jirislaby@gmail.com>, kernelnewbies@nl.linux.org, linux-kernel@vger.kernel.org, linux-embedded@vger.kernel.org

On Sun, Nov 22, 2009 at 10:14 PM, Johnny Hung <johnny.hacking@gmail.com=
> wrote:
> After testing:
>
> # gcc inlineasm.c
> inlineasm.c: Assembler messages:
> inlineasm.c:7: Error: suffix or operands invalid for `out'
> [root@debian-johnny] ~/workspace/test
>
> # cat inlineasm.c
> #include <stdio.h>
>
> int main ()
> {
> =C2=A0 =C2=A0unsigned int val =3D 5, tmp =3D 10;
> =C2=A0 =C2=A0asm volatile ("outb $0x27, %%al"
> =C2=A0 =C2=A0 :
> =C2=A0 =C2=A0 : "a" (0xb2), "b"(val), "c" (tmp)
> =C2=A0 =C2=A0);
> }
>
> =C2=A0 =C2=A0It seems the source of outb instruction cannot be a cons=
tant. Is
> there a AT&T instructions document for x86?

In AT&T syntax, the source register comes first.  So it should be
"outb %%al, $0x27", assuming that 0x27 is the port number you are
trying to write to.

--
Brian Gerst