38 lines
1.1 KiB
C
38 lines
1.1 KiB
C
|
#include "ports.h"
|
||
|
|
|
||
|
|
/**
|
||
|
|
* Read a byte from the specified port
|
||
|
|
*/
|
||
|
|
u8 port_byte_in (u16 port) {
|
||
|
|
u8 result;
|
||
|
|
/* Inline assembler syntax
|
||
|
|
* !! Notice how the source and destination registers are switched from NASM !!
|
||
|
|
*
|
||
|
|
* '"=a" (result)'; set '=' the C variable '(result)' to the value of register e'a'x
|
||
|
|
* '"d" (port)': map the C variable '(port)' into e'd'x register
|
||
|
|
*
|
||
|
|
* Inputs and outputs are separated by colons
|
||
|
|
*/
|
||
|
|
__asm__("in %%dx, %%al" : "=a" (result) : "d" (port));
|
||
|
|
return result;
|
||
|
|
}
|
||
|
|
|
||
|
|
void port_byte_out (u16 port, u8 data) {
|
||
|
|
/* Notice how here both registers are mapped to C variables and
|
||
|
|
* nothing is returned, thus, no equals '=' in the asm syntax
|
||
|
|
* However we see a comma since there are two variables in the input area
|
||
|
|
* and none in the 'return' area
|
||
|
|
*/
|
||
|
|
__asm__ __volatile__("out %%al, %%dx" : : "a" (data), "d" (port));
|
||
|
|
}
|
||
|
|
|
||
|
|
u16 port_word_in (u16 port) {
|
||
|
|
u16 result;
|
||
|
|
__asm__("in %%dx, %%ax" : "=a" (result) : "d" (port));
|
||
|
|
return result;
|
||
|
|
}
|
||
|
|
|
||
|
|
void port_word_out (u16 port, u16 data) {
|
||
|
|
__asm__ __volatile__("out %%ax, %%dx" : : "a" (data), "d" (port));
|
||
|
|
}
|