Create module uart

src/main.rs

@@ -4,6 +4,8 @@
 
 use core::panic::PanicInfo;
 
+mod uart;
+
 #[naked]
 #[no_mangle]
 #[link_section = ".text.init"]
@@ -28,20 +30,10 @@ unsafe extern "C" fn _start() -> ! {
 }
 
 extern "C" fn entry() -> ! {
-    use core::ptr::write_volatile;
+    // UNSAFE: correct address for QEMU virt device
-    let addr = 0x1000_0000 as *mut u8;
+    let mut console = unsafe { uart::Device::new(0x1000_0000) };
-    {
+    for byte in "Hello, world!".bytes() {
-        // Set data size to 8 bits.
+        console.put(byte);
-        unsafe { write_volatile(addr.offset(3), 0b11) };
-        // Enable FIFO.
-        unsafe { write_volatile(addr.offset(2), 0b1) };
-        // Enable receiver buffer interrupts.
-        unsafe { write_volatile(addr.offset(1), 0b1) };
-    }
-
-    // UART is now set up! Let's print a message.
-    for byte in "Hello, world!\n".bytes() {
-        unsafe { write_volatile(addr, byte) };
     }
 
     loop {}

src/uart.rs

@@ -0,0 +1,32 @@
+//! This module provides access to the UART console.
+
+/// Represents an initialised UART device.
+pub struct Device {
+    base: usize,
+}
+
+impl Device {
+    /// Create a new UART device.
+    /// # Safety
+    /// `base` must be the base address of a UART device.
+    pub unsafe fn new(base: usize) -> Self {
+        use core::ptr::write_volatile;
+        let addr = base as *mut u8;
+        // Set data size to 8 bits.
+        unsafe { write_volatile(addr.offset(3), 0b11) };
+        // Enable FIFO.
+        unsafe { write_volatile(addr.offset(2), 0b1) };
+        // Enable receiver buffer interrupts.
+        unsafe { write_volatile(addr.offset(1), 0b1) };
+        // Return a new, initialised UART device.
+        Device { base }
+    }
+
+    pub fn put(&mut self, character: u8) {
+        let ptr = self.base as *mut u8;
+        // UNSAFE: fine as long as self.base is valid
+        unsafe {
+            core::ptr::write_volatile(ptr, character);
+        }
+    }
+}