#include <kernel.h>
#include "serial.h"

void outb(int port, unsigned char data)
{
    __asm__ __volatile__("outb %%al, %%dx" :: "a" (data),"d" (port));
}

unsigned char inb(int port)
{
    unsigned char data = 0;
    __asm__ __volatile__("inb %%dx, %%al" : "=a" (data) : "d" (port));
    return data;
}

// COM1
#define PORT 0x3F8

int serial_init()
{
    outb(PORT + 1, 0x00);      // Disable all interrupts
    outb(PORT + 3, 0x80);    // Enable DLAB (set baud rate divisor)
    outb(PORT + 0, 0x03);    // Set divisor to 3 (lo byte) 38400 baud
    outb(PORT + 1, 0x00);    //                  (hi byte)
    outb(PORT + 3, 0x03);    // 8 bits, no parity, one stop bit
    outb(PORT + 2, 0xC7);    // Enable FIFO, clear them, with 14-byte threshold
    outb(PORT + 4, 0x0B);    // IRQs enabled, RTS/DSR set
    outb(PORT + 4, 0x1E);    // Set in loopback mode, test the serial chip
    outb(PORT + 0, 0xAE);    // Test serial chip (send byte 0xAE and check if serial returns same byte)

    if (inb(PORT) != 0xAE)
    {
        return -EIO;
    }

    // Set normal operation mode
    outb(PORT + 4, 0x0F);

    DEBUG("serial initialized");
    return 0;
}

static int is_transmit_empty()
{
    return inb(PORT + 5) & 0x20;
}

// Serial kernel putchar
void skputc(char c)
{
    while (!is_transmit_empty()); // wait for free spot
    outb(PORT, c);
}

// Serial kernel putstring
void skputs(const char* str)
{
    unsigned int i=0;
    while (str[i])
    {
        skputc(str[i]);
        i++;
    }
}