1 files changed, 45 insertions, 1 deletions

diff --git a/src/io.c b/src/io.c
index 1d9db60..d1206c3 100644
--- a/src/io.c
+++ b/src/io.c
@@ -1,6 +1,10 @@
 #include <stdint.h>
 #include "utils.h"
 
+#define PORT 0x3f8                   // COM1
+#define LINE_STATUS_REGISTER         PORT + 5
+#define TRANSMITTER_EMPTY_BITMASK    0b00100000
+
 uint8_t inportb(uint16_t port) {
     uint8_t r;
     asm("inb %1, %0" : "=a" (r) : "dN" (port));
@@ -9,4 +13,44 @@ uint8_t inportb(uint16_t port) {
 
 void outportb(uint16_t port, uint8_t data) {
     asm("outb %1, %0" : : "dN" (port), "a" (data));
-}
\ No newline at end of file
+}
+
+void init_serial() {
+    outportb(PORT + 1, 0x00); // Disable all interrupts
+    outportb(PORT + 3, 0x80); // Enable DLAB (set baud rate divisor)
+
+    // Set divisor to 3 -> (115200 / 3) = 38400
+    outportb(PORT + 0, 0x03); // LSB
+    outportb(PORT + 1, 0x00); // MSB
+
+    outportb(PORT + 3, 0x03); // Character length is 8 bits, no parity, one stop bit
+    outportb(PORT + 2, 0xC7); // Enable FIFO, clear them, with 14-byte threshold
+
+//  TODO: GDT and IDT in order to setup COM1 interrupts.
+//        For now, though, we POLLLLL that mf.
+//     outportb(PORT + 4, 0x0B); // IRQs enabled, RTS/DSR set
+
+    outportb(PORT + 4, 0x1E); // Set in loopback mode, test the serial chip
+    outportb(PORT + 0, 0xAE); // Test serial chip (send byte 0xAE and check if serial returns same byte)
+    macaroni_assert(inportb(PORT + 0) == 0xAE, "0xAE expected from serial initizliation");
+    outportb(PORT + 4, 0x0F);
+}
+
+int serial_tx_empty(void) {
+    return inportb(LINE_STATUS_REGISTER) & TRANSMITTER_EMPTY_BITMASK;
+}
+
+void serial_putc(char c) {
+    while (!serial_tx_empty());
+    outportb(PORT, c);
+}
+
+void serial_puts(const char* s) {
+    while (*s) serial_putc(*s++);
+}
+
+void serial_puthex(uint32_t h) {
+    serial_puts("0x");
+    for (int i = 28; i >= 0; i -= 4)
+        serial_putc("0123456789abcdef"[(h >> i) & 0xF]);
+}