eonix/src/kernel/hw/serial.c

#include <kernel/hw/serial.h>
#include <asm/port_io.h>

int32_t init_serial_port(port_id_t port)
{
    // taken from osdev.org

   asm_outb(port + 1, 0x00);    // Disable all interrupts
   asm_outb(port + 3, 0x80);    // Enable DLAB (set baud rate divisor)
   // TODO: set baud rate
   asm_outb(port + 0, 0x00);    // Set divisor to 0 -3- (lo byte) 115200 -38400- baud
   asm_outb(port + 1, 0x00);    //                  (hi byte)
   asm_outb(port + 3, 0x03);    // 8 bits, no parity, one stop bit
   asm_outb(port + 2, 0xC7);    // Enable FIFO, clear them, with 14-byte threshold
   asm_outb(port + 4, 0x0B);    // IRQs enabled, RTS/DSR set
   asm_outb(port + 4, 0x1E);    // Set in loopback mode, test the serial chip
   asm_outb(port + 0, 0xAE);    // Test serial chip (send byte 0xAE and check if serial returns same byte)

   // Check if serial is faulty (i.e: not same byte as sent)
   if(asm_inb(port + 0) != 0xAE) {
      return 1;
   }

   // If serial is not faulty set it in normal operation mode
   // (not-loopback with IRQs enabled and OUT#1 and OUT#2 bits enabled)
   asm_outb(port + 4, 0x0F);
   return 0;
}

int32_t is_serial_has_data(port_id_t port)
{
    return asm_inb(port + 5) & 1;
}

uint8_t serial_read_data(port_id_t port)
{
    while (is_serial_has_data(port) == 0)
        ;
    return asm_inb(port);
}

int32_t is_serial_ready_for_transmition(port_id_t port)
{
    return asm_inb(port + 5) & 0x20;
}

void serial_send_data(port_id_t port, uint8_t data)
{
    while (is_serial_ready_for_transmition(port) == 0)
        ;
    return asm_outb(port, data);
}