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Re: Bloody Beginner 2: __asm volatile
Posted: Thu Jul 10, 2008 1:37 pm
by hpclutz
Great, guys!!!
Thanks to all your help I got it working now with
Code: Select all
char inportb(short port)
{
char ret_val;
_asm {
mov dx, port
in al, dx
mov ret_val, al
}
return ret_val;
}
So I got myself a neat little Command Line Interface with update cursor and everything ready, though I don't yet do more than just print the characters I type - nonetheless, it works
Thanks guys, don't know what I would have done without you all
(and I'm sure to be back with the next topic soon
)
Re: Bloody Beginner 2: __asm volatile
Posted: Thu Jul 10, 2008 2:22 pm
by Adek336
cr2 wrote:Code: Select all
char inb (short port) {
char val;
__asm {
mov dx, port
in eax, dx
mov val, al
}
return val;
}
EAX is 4-byte long; so this code actually reads 4 bytes from a port (instead of one byte). so "al" instead of "eax" is grand
Re: Bloody Beginner 2: __asm volatile
Posted: Thu Jul 10, 2008 2:26 pm
by Omega
That's great man, good job on getting your KBC Driver working!
Re: Bloody Beginner 2: __asm volatile
Posted: Fri Jul 11, 2008 7:48 am
by Solar
Just for the records, TR18015 and TR18037 added this nice tidbit to the C library:
Code: Select all
#include <iohw.h>
unsigned int iord( ioreg dev );
Why am I mentioning this? Two reasons:
1) If you happen to have an up-to-date C library ported to your system, you can use iord() instead of writing your own function with inline assembly.
I admit that's a fat chance, so how about...
2) if you write your function with inline assembly, why not call it
iord() (instead of
inb()) and declare it in a header called
<iohw.h>?