Move dts to board dir, fix some import error

Signed-off-by: Harry Chen <i@harrychen.xyz>

kernel/Makefile

@@ -49,20 +49,22 @@ user_dir := ../user
 
 
 ### export environments ###
-export ARCH = $(arch)
-export BOARD = $(board)
-export SMP = $(smp)
-export DTB = $(dtb)
 export SFSIMG = $(user_dir)/build/$(arch).qcow2
 
 ifeq ($(arch), aarch64)
 board := raspi3
 export SFSIMG = $(user_dir)/build/$(arch).img
-else ifeq ($(arch), mipsel)
-board := malta
 endif
 
-dtb := src/arch/$(arch)/boot/dts/$(board).dtb
+# currently only mipsel architecture needs DTB linked to the kernel
+ifeq ($(arch), mipsel)
+dtb := src/arch/$(arch)/board/$(board)/device.dtb
+endif
+
+export ARCH = $(arch)
+export BOARD = $(board)
+export SMP = $(smp)
+export DTB = $(dtb)
 
 
 ### qemu options ###

kernel/src/arch/mipsel/board/malta/fb.rs

@@ -1,3 +1,7 @@
+//! stub frame buffer driver for malta board
+
+use spin::Mutex;
+
 lazy_static! {
     pub static ref FRAME_BUFFER: Mutex<Option<Framebuffer>> = Mutex::new(None);
 }

kernel/src/arch/mipsel/board/malta/serial.rs

@@ -1,5 +1,8 @@
+//! 16550 serial adapter driver for malta board
+
 use core::fmt::{Write, Result, Arguments};
 use core::ptr::{read_volatile, write_volatile};
+use spin::Mutex;
 
 struct SerialPort {
     base: usize
@@ -7,7 +10,9 @@ struct SerialPort {
 
 impl SerialPort {
     fn new() -> SerialPort {
-        SerialPort { }
+        SerialPort { 
+            base: 0
+        }
     }
 
     pub fn init(&mut self, base: usize) {

kernel/src/arch/mipsel/interrupt.rs

@@ -1,5 +1,5 @@
-use mips::interrupts::*;
-use mips::registers::*;
+use mips::interrupts;
+use mips::registers::cp0;
 use crate::drivers::DRIVERS;
 pub use self::context::*;
 use log::*;

kernel/src/arch/mipsel/io.rs

@@ -9,7 +9,7 @@ pub fn getchar() -> char {
     SERIAL_PORT.lock().getchar()
 }
 
-pub fn getchar_option() -> Option<Char> {
+pub fn getchar_option() -> Option<char> {
     unsafe { SERIAL_PORT.force_unlock() }
     SERIAL_PORT.lock().getchar_option()
 }

kernel/src/arch/mipsel/mod.rs

@@ -11,7 +11,7 @@ pub mod rand;
 pub mod driver;
 
 use log::*;
-use mips::registers;
+use mips::registers::cp0;
 use mips::instructions;
 
 #[cfg(feature = "board_malta")]