Meta: Move kernel and userland to their own folders.

This is to allow both the kernel and the userland to share certain
header files and to make the folder structure a bit more clear.

1 files changed, 35 insertions, 0 deletions

diff --git a/kernel/drivers/serial.c b/kernel/drivers/serial.c
new file mode 100644
index 0000000..549d852
--- /dev/null
+++ b/kernel/drivers/serial.c
@@ -0,0 +1,35 @@
+#include "cpu/io.h"
+
+#define PORT 0x3f8 // COM1
+
+int serial_init(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)
+
+  // 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);
+  return 0;
+}
+
+int is_transmit_empty() { return inb(PORT + 5) & 0x20; }
+
+void write_serial(char a) {
+  while (is_transmit_empty() == 0)
+    ;
+
+  outb(PORT, a);
+}