1 files changed, 40 insertions, 0 deletions
diff --git a/kernel/hal/io.c b/kernel/hal/io.c
new file mode 100644
index 0000000..d97a211
--- /dev/null
+++ b/kernel/hal/io.c
@@ -0,0 +1,40 @@
+#include "kernel.h"
+
+// Write a byte to an I/O port.
+void 
+out(WORD port, BYTE value )
+{
+    __asm__ __volatile__ (
+	"outb %b0, %w1"
+	:
+	: "a" (value), "Nd" (port)
+    );
+}
+
+// Read a byte from an I/O port.
+BYTE 
+in(WORD port)
+{
+    BYTE value;
+
+    __asm__ __volatile__ (
+	"inb %w1, %b0"
+	: "=a" (value)
+	: "Nd" (port)
+    );
+
+    return value;
+}
+
+// Short delay.  May be needed when talking to some
+// (slow) I/O devices.
+void 
+iodelay(void)
+{
+    BYTE value = 0;
+    __asm__ __volatile__ (
+	"outb %0, $0x80"
+	:
+	: "a" (value)
+    );
+}