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/*
* CMOS
* Copyright (C) 2024-2025 Raghuram Subramani <raghus2247@gmail.com>
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include <libk/string.h>
#include <kernel/io.h>
#include <drivers/serial.h>
/* Implementation adapted from
* https://wiki.osdev.org/Inline_Assembly/Examples */
void
serial_initialize(void)
{
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)
// TODO: Check if serial is faulty (i.e: not same byte as sent)
/* if (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)
outb(PORT + 4, 0x0F);
}
static int
is_transmit_empty()
{
return inb(PORT + 5) & 0x20;
}
void
serial_write_char(const char a)
{
while (is_transmit_empty() == 0)
;
outb(PORT, a);
}
void
serial_write_string(const char *string)
{
size_t size = strlen(string);
for (size_t i = 0; i < size; i++)
serial_write_char(string[i]);
}
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