feat(drivers): add port I/O helpers and serial COM1 driver

include/ports.h

@@ -0,0 +1,65 @@
+#ifndef FROSTBYTE_PORTS_H
+#define FROSTBYTE_PORTS_H
+
+#include "types.h"
+
+static inline void outb(uint16 port, uint8 value)
+{
+    __asm__ volatile("outb %0, %1" : : "a"(value), "Nd"(port));
+}
+
+static inline uint8 inb(uint16 port)
+{
+    uint8 value;
+    __asm__ volatile("inb %1, %0" : "=a"(value) : "Nd"(port));
+    return value;
+}
+
+static inline void outw(uint16 port, uint16 value)
+{
+    __asm__ volatile("outw %0, %1" : : "a"(value), "Nd"(port));
+}
+
+static inline uint16 inw(uint16 port)
+{
+    uint16 value;
+    __asm__ volatile("inw %1, %0" : "=a"(value) : "Nd"(port));
+    return value;
+}
+
+static inline void ioWait(void)
+{
+    outb(0x80, 0);
+}
+
+static inline uint64 readFlags(void)
+{
+    uint64 flags;
+    __asm__ volatile("pushfq; popq %0" : "=r"(flags));
+    return flags;
+}
+
+static inline void enableInterrupts(void)
+{
+    __asm__ volatile("sti");
+}
+
+static inline uint64 saveAndDisableInterrupts(void)
+{
+    uint64 flags = readFlags();
+    __asm__ volatile("cli");
+    return flags;
+}
+
+static inline void restoreInterrupts(uint64 flags)
+{
+    if (flags & (1u << 9))
+        __asm__ volatile("sti");
+}
+
+static inline void halt(void)
+{
+    __asm__ volatile("hlt");
+}
+
+#endif

include/serial.h

@@ -0,0 +1,10 @@
+#ifndef FROSTBYTE_SERIAL_H
+#define FROSTBYTE_SERIAL_H
+
+#include "types.h"
+
+void serialInit(void);
+void serialWrite(char c);
+void serialWriteString(const char* str);
+
+#endif

src/serial.c

@@ -0,0 +1,36 @@
+#include "serial.h"
+#include "ports.h"
+
+#define comPort1 0x3F8
+
+static bool transmitEmpty(void)
+{
+    return (inb(comPort1 + 5) & 0x20) != 0;
+}
+
+void serialInit(void)
+{
+    outb(comPort1 + 1, 0x00);
+    outb(comPort1 + 3, 0x80);
+    outb(comPort1 + 0, 0x01);
+    outb(comPort1 + 1, 0x00);
+    outb(comPort1 + 3, 0x03);
+    outb(comPort1 + 2, 0xC7);
+    outb(comPort1 + 4, 0x0B);
+}
+
+void serialWrite(char c)
+{
+    if (c == '\n') {
+        while (!transmitEmpty()) { }
+        outb(comPort1, '\r');
+    }
+    while (!transmitEmpty()) { }
+    outb(comPort1, (uint8)c);
+}
+
+void serialWriteString(const char* str)
+{
+    while (*str)
+        serialWrite(*str++);
+}