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#include <comus/drivers/uart.h>
#include <comus/asm.h>
#define PORT 0x3F8
int uart_init(void) {
outb(PORT + 1, 0x00); // disable interrupts
outb(PORT + 3, 0x80); // enable DLAB (divisor latch access bit)
outb(PORT + 0, 0x03); // (lo) Set baud divisor to 3 38400 baud
outb(PORT + 1, 0x00); // (hi)
outb(PORT + 3, 0x03); // disable DLAB, set 8 bits per word, one stop bit, no parity
outb(PORT + 2, 0xC7); // enable and clear FIFOs, set to maximum threshold
outb(PORT + 4, 0x0B); // ???
outb(PORT + 4, 0x1E); // set in loopback mode for test
outb(PORT + 0, 0xAE); // test by sending 0xAE
uint8_t response = inb(PORT + 0);
if (response != 0xAE) {
// TODO: panic here?
return -1;
}
// disable loopback, enable IRQs
outb(PORT + 4, 0x0F);
return 0;
}
uint8_t uart_in(void) {
// wait for data to be available
while ((inb(PORT + 5) & 0x01) == 0);
return inb(PORT);
}
void uart_out(uint8_t ch) {
// wait for output to be free
while ((inb(PORT + 5) & 0x20) == 0);
outb(PORT, ch);
}
void uart_out_str(const char *str) {
while (*str)
uart_out(*str++);
}
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