[Nasm-users] access to serial port

[<ada...@t-...>]

> Hi Michael,
>
> Sorry for the delay. Took a while before I got around to booting Linux
> and fooling with this. I have *no* idea how to send data to a serial
> port - "everything's a file", they say, maybe you can just open a file
> and write bytes(???). (might even be able to redirect stdout to a serial
> port?)
>........
> Best,
> Frank

Hello Frank

It is possible to blow a hole in the 'Protected mode' of Linux. I use the 'C
function' called 'ioperm' to communicate with the serial port 0x2f8 the way
like this:

.......
push word 1                      ;enable 'ioperm'
push dword 8                    ;8 bytes of the serial port register
push dword port                ;port adress
call ioperm
add esp, 10
......
'in' and 'out' to the serial port IC 16450 or similar
......
push word 0                      ;disable 'ioperm'
push dword 8                    ;8 bytes of the serial port register
push dword port                ;port adress
call ioperm
add esp, 10


Michael Adam