karlos/karlos
7
1
Fork 0
Code Issues 3 Pull requests Projects Releases Packages Wiki Activity Actions

Wrote a very simple UART driver together

Browse source
This commit is contained in:
Thomas Oltmann 2025-01-16 00:16:46 +01:00
parent 488bf0ce0a
commit 6fcb55bdd8
3 changed files with 39 additions and 1 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

2
Makefile
View file

@ -6,7 +6,7 @@ include config.mk
# Add new source files (C or Assembler) here,
# preferentially in alphabetical order.
KERNEL_SOURCES_x86_64 := \
x86_64/init.S \
x86_64/uart.c \
# end of x86_64 specific kernel sources list
# Architecture-agnostic kernel sources.

4
kernel.c
View file

@ -40,6 +40,8 @@ typedef unsigned long int uint64_t;
#include "bootboot.h"
extern void write_string(const char *string);
/* imported virtual addresses, see linker script */
extern BOOTBOOT bootboot; // see bootboot.h
extern unsigned char environment[4096]; // configuration, UTF-8 text key=value pairs
@ -88,6 +90,8 @@ extern volatile unsigned char _binary_font_psf_start;
void puts(char *s)
{
write_string(s);
psf2_t *font = (psf2_t*)&_binary_font_psf_start;
int x,y,kx=0,line,mask,offs;
int bpl=(font->width+7)/8;

34
x86_64/uart.c Normal file
View file

@ -0,0 +1,34 @@
#define COM1_BASE_PORT 0x3F8
int
inb(int port)
{
unsigned char value;
__asm__ ("inb %%dx" : "=a"(value) : "d"(port));
return value;
}
void
outb(int port, int value)
{
__asm__ ("outb %%dx" :: "d"(port), "a"(value));
}
void
write_char(char c)
{
while (1) {
int line_status = inb(COM1_BASE_PORT + 5);
if (line_status & 0x20) break;
}
outb(COM1_BASE_PORT, c);
}
void
write_string(const char *string)
{
for (const char *c = string; *c != 0; c++) {
write_char(*c);
}
}