Rename the src directory to kernel.

kernel/arch/x86_64/io/mmio.rs

@@ -0,0 +1,31 @@
+use core::intrinsics::{volatile_load, volatile_store};
+use core::mem::uninitialized;
+use core::ops::{BitAnd, BitOr, Not};
+
+use super::io::Io;
+
+#[repr(packed)]
+pub struct Mmio<T> {
+    value: T,
+}
+
+impl<T> Mmio<T> {
+    /// Create a new Mmio without initializing
+    pub fn new() -> Self {
+        Mmio {
+            value: unsafe { uninitialized() }
+        }
+    }
+}
+
+impl<T> Io for Mmio<T> where T: Copy + PartialEq + BitAnd<Output = T> + BitOr<Output = T> + Not<Output = T> {
+    type Value = T;
+
+    fn read(&self) -> T {
+        unsafe { volatile_load(&self.value) }
+    }
+
+    fn write(&mut self, value: T) {
+        unsafe { volatile_store(&mut self.value, value) };
+    }
+}