Inline assembly and using of IN and OUT assembler instructions

Inline assembly and using of IN and OUT assembler instructions

[majess]

Hello,all
I've written two functions, which are responsible for writing and 
reading byte(8 bit char) from I/O space of x86 architecture processor 
(IBM T23 Pentium III laptop.).I need that functions to write drivers to 
use COM1(RS232) under Debian and utilizing GCC compiler. I have to work 
on registers.......and I can't use BIOS functions.

I'm using GNU/Debian operating system and GCC (ver. for Debian 4:4.0.2-2)
Below are presented functions which I wrote:

void OutPort(unsigned short int IO_port,char Value)
{
    asm("outb %%al,%%dx;"
    : //no output data
    :"d"(IO_port),"a"(Value) //input data (EDX<-IO_port; AL<-Value)
    );
}
char InPort(unsigned short int IO_port)
{
    asm("inb %%dx,%%al;"
    : //output data is in al register
    :"d"(IO_port) //input data (EDX<-IO_port AL<-Value)
    );
}

/*      Intel Syntax
        OUT PORT
        mov dx,IOport
        mov al,Value
        out dx,al
        IN PORT
        mov dx,IOport
        in al,dx
        mov rueck,al
*/
That functions with other code are compiled with GCC Compiler, but the 
program behaves like it execute operations to the moment when it 
encounter, for example InPort(0x3f0) or OutPort(0x3f0,'s'); statement 
and statements after that aren't performed.
I'd also say that I was using HOW-TO doc about GCC and inline 
assembly(http://www.ibiblio.org/gferg/ldp/GCC-Inline-Assembly-HOWTO.html) 
as a manual.

To sum up:
Maybe somebody know how to fix that functions to work properly under GCC 
and Debian (maybe they don't work because of Debian restrictions to I/O 
space access ?)
Maybe one of this mailing group member has similar problem?
I will be very grateful for help.

Best regards,
Lukasz Majewski