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
