serial: Use lazy_static crate

The recent version of Rust does not allow runtime calls in statics. This
commit adds lazy_static crate to mitigate this limitation.

Signed-off-by: Akira Moroo <[email protected]>

Author: retrage

Cargo.toml

@@ -24,6 +24,10 @@ log-serial = []
 log-panic = ["log-serial"]
 integration_tests = []
 
+[dependencies.lazy_static]
+version = "1.4.0"
+features = ["spin_no_std"]
+
 [dependencies]
 bitflags = "1.2"
 x86_64 = "0.12"

src/serial.rs

@@ -18,10 +18,14 @@
 use core::fmt;
 
 use atomic_refcell::AtomicRefCell;
+use lazy_static::lazy_static;
 use uart_16550::SerialPort;
 
 // We use COM1 as it is the standard first serial port.
-pub static PORT: AtomicRefCell<SerialPort> = AtomicRefCell::new(unsafe { SerialPort::new(0x3f8) });
+lazy_static! {
+    pub static ref PORT: AtomicRefCell<SerialPort> =
+        AtomicRefCell::new(unsafe { SerialPort::new(0x3f8) });
+}
 
 pub struct Serial;
 impl fmt::Write for Serial {