i386: add serial port support

Add support for serial communication in the i386 architecture.

Signed-off-by: Danny Holman <dholman@gymli.xyz>

3 files changed, 57 insertions, 0 deletions

diff --git a/arch/i386/make.config b/arch/i386/make.config
index a5049af..680760f 100644
--- a/arch/i386/make.config
+++ b/arch/i386/make.config
@@ -4,3 +4,4 @@ KERNEL_ARCH_LIBS=
 
 KERNEL_ARCH_OBJS=$(ARCHDIR)/boot.o \
                  $(ARCHDIR)/tty.o \
+                 $(ARCHDIR)/serial.o \
diff --git a/arch/i386/pic.h b/arch/i386/pic.h
new file mode 100644
index 0000000..da4a2ee
--- /dev/null
+++ b/arch/i386/pic.h
@@ -0,0 +1,16 @@
+#ifndef PIC_H
+#define PIC_H
+
+#include <stdint.h>
+
+static inline void outb(uint16_t port, uint8_t value) {
+        asm volatile("outb %0, %1" : : "a"(value), "Nd"(port));
+}
+
+static inline uint8_t inb(uint16_t port) {
+        uint8_t ret;
+        asm volatile("inb %1, %0" : "=a"(ret) : "Nd"(port));
+        return ret;
+}
+
+#endif
diff --git a/arch/i386/serial.c b/arch/i386/serial.c
new file mode 100644
index 0000000..b172e82
--- /dev/null
+++ b/arch/i386/serial.c
@@ -0,0 +1,40 @@
+#include <kernel/serial.h>
+#include "pic.h"
+
+#define PORT 0x3f8
+
+static int serial_init(void) {
+        outb(PORT + 1, 0x00);
+        outb(PORT + 3, 0x80);
+        outb(PORT + 0, 0x03);
+        outb(PORT + 1, 0x00);
+        outb(PORT + 3, 0x03);
+        outb(PORT + 2, 0xC7);
+        outb(PORT + 4, 0x0B);
+        outb(PORT + 4, 0x1E);
+        outb(PORT + 0, 0xAE);
+
+        if (inb(PORT + 0) != 0xAE)
+                return -1;
+
+        outb(PORT + 4, 0x0F);
+        return 0;
+}
+
+int serial_recieved(void) {
+        return inb(PORT + 5) & 1;
+}
+
+char read_serial(void) {
+        while (serial_recieved() == 0);
+        return inb(PORT);
+}
+
+int is_transmit_empty(void) {
+        return inb(PORT + 5) & 0x20;
+}
+
+void write_serial(char a) {
+        while (is_transmit_empty() == 0);
+        outb(PORT, a);
+}