Ability to manipulate palettes

src/colors.rs

@@ -1,5 +1,7 @@
 //! Common color structures used in vga.
 
+pub const PALETTE_SIZE: usize = 768;
+
 /// Represents a 16 bit color used for vga display.
 #[derive(Debug, Clone, Copy)]
 #[repr(u8)]
@@ -50,3 +52,55 @@ impl TextModeColor {
         TextModeColor((background as u8) << 4 | (foreground as u8))
     }
 }
+
+/// Represents the default vga 256 color palette.
+pub const DEFAULT_PALETTE: [u8; PALETTE_SIZE] = [
+    0x0, 0x0, 0x0, 0x0, 0x0, 0x2A, 0x0, 0x2A, 0x0, 0x0, 0x2A, 0x2A, 0x2A, 0x0, 0x0, 0x2A, 0x0,
+    0x2A, 0x2A, 0x2A, 0x0, 0x2A, 0x2A, 0x2A, 0x0, 0x0, 0x15, 0x0, 0x0, 0x3F, 0x0, 0x2A, 0x15, 0x0,
+    0x2A, 0x3F, 0x2A, 0x0, 0x15, 0x2A, 0x0, 0x3F, 0x2A, 0x2A, 0x15, 0x2A, 0x2A, 0x3F, 0x0, 0x15,
+    0x0, 0x0, 0x15, 0x2A, 0x0, 0x3F, 0x0, 0x0, 0x3F, 0x2A, 0x2A, 0x15, 0x0, 0x2A, 0x15, 0x2A, 0x2A,
+    0x3F, 0x0, 0x2A, 0x3F, 0x2A, 0x0, 0x15, 0x15, 0x0, 0x15, 0x3F, 0x0, 0x3F, 0x15, 0x0, 0x3F,
+    0x3F, 0x2A, 0x15, 0x15, 0x2A, 0x15, 0x3F, 0x2A, 0x3F, 0x15, 0x2A, 0x3F, 0x3F, 0x15, 0x0, 0x0,
+    0x15, 0x0, 0x2A, 0x15, 0x2A, 0x0, 0x15, 0x2A, 0x2A, 0x3F, 0x0, 0x0, 0x3F, 0x0, 0x2A, 0x3F,
+    0x2A, 0x0, 0x3F, 0x2A, 0x2A, 0x15, 0x0, 0x15, 0x15, 0x0, 0x3F, 0x15, 0x2A, 0x15, 0x15, 0x2A,
+    0x3F, 0x3F, 0x0, 0x15, 0x3F, 0x0, 0x3F, 0x3F, 0x2A, 0x15, 0x3F, 0x2A, 0x3F, 0x15, 0x15, 0x0,
+    0x15, 0x15, 0x2A, 0x15, 0x3F, 0x0, 0x15, 0x3F, 0x2A, 0x3F, 0x15, 0x0, 0x3F, 0x15, 0x2A, 0x3F,
+    0x3F, 0x0, 0x3F, 0x3F, 0x2A, 0x15, 0x15, 0x15, 0x15, 0x15, 0x3F, 0x15, 0x3F, 0x15, 0x15, 0x3F,
+    0x3F, 0x3F, 0x15, 0x15, 0x3F, 0x15, 0x3F, 0x3F, 0x3F, 0x15, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F,
+    0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F,
+    0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F,
+    0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F,
+    0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F,
+    0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F,
+    0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F,
+    0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F,
+    0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F,
+    0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F,
+    0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F,
+    0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F,
+    0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F,
+    0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F,
+    0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F,
+    0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F,
+    0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F,
+    0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F,
+    0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F,
+    0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F,
+    0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F,
+    0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F,
+    0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F,
+    0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F,
+    0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F,
+    0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F,
+    0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F,
+    0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F,
+    0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F,
+    0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F,
+    0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F,
+    0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F,
+    0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F,
+    0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F,
+    0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F,
+    0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F,
+    0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F,
+];

src/lib.rs

@@ -14,6 +14,7 @@ mod registers;
 mod vga;
 mod writers;
 
+pub use self::colors::{Color16Bit, TextModeColor, DEFAULT_PALETTE, PALETTE_SIZE};
 pub use self::configurations::{
     VgaConfiguration, MODE_40X25_CONFIGURATION, MODE_40X50_CONFIGURATION,
     MODE_640X480X16_CONFIGURATION, MODE_80X25_CONFIGURATION,

src/registers.rs

@@ -1,3 +1,4 @@
+use crate::colors::PALETTE_SIZE;
 use x86_64::instructions::port::{Port, PortReadOnly, PortWriteOnly};
 
 const ST00_READ_ADDRESS: u16 = 0x3C2;
@@ -23,6 +24,10 @@ const CRX_INDEX_MDA_ADDRESS: u16 = 0x3B4;
 const CRX_DATA_CGA_ADDRESS: u16 = 0x3D5;
 const CRX_DATA_MDA_ADDRESS: u16 = 0x3B5;
 
+const COLOR_PALETTE_DATA_ADDRESS: u16 = 0x3C9;
+const COLOR_PALETTE_INDEX_READ_ADDRESS: u16 = 0x3C7;
+const COLOR_PALETTE_INDEX_WRITE_ADDRESSS: u16 = 0x3C8;
+
 #[derive(Debug, Copy, Clone)]
 #[repr(u8)]
 pub enum EmulationMode {
@@ -389,3 +394,42 @@ impl CrtcControllerRegisters {
         }
     }
 }
+
+#[derive(Debug)]
+pub struct ColorPaletteRegisters {
+    data_port: Port<u8>,
+    index_read_port: Port<u8>,
+    index_write_port: Port<u8>,
+}
+
+impl ColorPaletteRegisters {
+    pub fn new() -> ColorPaletteRegisters {
+        ColorPaletteRegisters {
+            data_port: Port::new(COLOR_PALETTE_DATA_ADDRESS),
+            index_read_port: Port::new(COLOR_PALETTE_INDEX_READ_ADDRESS),
+            index_write_port: Port::new(COLOR_PALETTE_INDEX_WRITE_ADDRESSS),
+        }
+    }
+
+    pub fn load_palette(&mut self, palette: &[u8; PALETTE_SIZE]) {
+        unsafe {
+            self.index_write_port.write(0);
+        }
+        for i in palette.iter() {
+            unsafe {
+                self.data_port.write(*i);
+            }
+        }
+    }
+
+    pub fn read_palette(&mut self, palette: &mut [u8; PALETTE_SIZE]) {
+        unsafe {
+            self.index_read_port.write(0);
+        }
+        for i in 0..PALETTE_SIZE {
+            unsafe {
+                palette[i] = self.data_port.read();
+            }
+        }
+    }
+}

src/vga.rs

@@ -1,15 +1,16 @@
 //! Provides access to the vga graphics card.
 
 use super::{
+    colors::PALETTE_SIZE,
     configurations::{
         VgaConfiguration, MODE_40X25_CONFIGURATION, MODE_40X50_CONFIGURATION,
         MODE_640X480X16_CONFIGURATION, MODE_80X25_CONFIGURATION,
     },
     fonts::{VgaFont, TEXT_8X16_FONT, TEXT_8X8_FONT},
     registers::{
-        AttributeControllerIndex, AttributeControllerRegisters, CrtcControllerIndex,
+        AttributeControllerIndex, AttributeControllerRegisters, ColorPaletteRegisters,
-        CrtcControllerRegisters, EmulationMode, GeneralRegisters, GraphicsControllerIndex,
+        CrtcControllerIndex, CrtcControllerRegisters, EmulationMode, GeneralRegisters,
-        GraphicsControllerRegisters, SequencerIndex, SequencerRegisters,
+        GraphicsControllerIndex, GraphicsControllerRegisters, SequencerIndex, SequencerRegisters,
     },
 };
 use conquer_once::spin::Lazy;
@@ -90,6 +91,7 @@ pub struct Vga {
     graphics_controller_registers: GraphicsControllerRegisters,
     attribute_controller_registers: AttributeControllerRegisters,
     crtc_controller_registers: CrtcControllerRegisters,
+    color_palette_registers: ColorPaletteRegisters,
     most_recent_video_mode: Option<VideoMode>,
 }
 
@@ -101,6 +103,7 @@ impl Vga {
             graphics_controller_registers: GraphicsControllerRegisters::new(),
             attribute_controller_registers: AttributeControllerRegisters::new(),
             crtc_controller_registers: CrtcControllerRegisters::new(),
+            color_palette_registers: ColorPaletteRegisters::new(),
             most_recent_video_mode: None,
         }
     }
@@ -172,6 +175,22 @@ impl Vga {
         EmulationMode::from(self.general_registers.read_msr() & 0x1)
     }
 
+    /// Loads a new palette into the vga, as specified by `palette`.
+    ///
+    /// Each palette must be `PALETTE_SIZE` bytes long, with every 3
+    /// bytes representing one color `(R, G, B)`.
+    pub fn load_palette(&mut self, palette: &[u8; PALETTE_SIZE]) {
+        self.color_palette_registers.load_palette(palette);
+    }
+
+    /// Reads the current vga palette into `palette`.
+    ///
+    /// Each palette must be `PALETTE_SIZE` bytes long, with every 3
+    /// bytes representing one color `(R, G, B)`.
+    pub fn read_palette(&mut self, palette: &mut [u8; PALETTE_SIZE]) {
+        self.color_palette_registers.read_palette(palette);
+    }
+
     fn load_font(&mut self, vga_font: &VgaFont) {
         // Save registers
         let (

src/writers/graphics_640x480x16.rs

@@ -1,5 +1,5 @@
 use crate::{
-    colors::Color16Bit,
+    colors::{Color16Bit, DEFAULT_PALETTE},
     vga::{Plane, Vga, VideoMode, VGA},
 };
 use spinning_top::SpinlockGuard;
@@ -34,6 +34,7 @@ impl Graphics640x480x16 {
 
     /// Clears the screen by setting all pixels to `Color16Bit::Black`.
     pub fn clear_screen(&self) {
+        // TODO: Clear the screen by using 4-plane mode instead of slow `set_pixel`.
         for x in 0..WIDTH {
             for y in 0..HEIGHT {
                 self.set_pixel(x, y, Color16Bit::Yellow);
@@ -72,7 +73,12 @@ impl Graphics640x480x16 {
 
     /// Sets the graphics device to `VideoMode::Mode640x480x16`.
     pub fn set_mode(&self) {
-        VGA.lock().set_video_mode(VideoMode::Mode640x480x16);
+        let mut vga = VGA.lock();
+        vga.set_video_mode(VideoMode::Mode640x480x16);
+
+        // Some bios mess up the palette when switching modes,
+        // so explicitly set it.
+        vga.load_palette(&DEFAULT_PALETTE);
     }
 
     /// Returns the start of the `FrameBuffer` as `*mut u8` as

src/writers/text_40x25.rs

@@ -1,6 +1,6 @@
 use super::ScreenCharacter;
 use crate::{
-    colors::{Color16Bit, TextModeColor},
+    colors::{Color16Bit, TextModeColor, DEFAULT_PALETTE},
     vga::{Vga, VideoMode, VGA},
 };
 use spinning_top::SpinlockGuard;
@@ -66,7 +66,12 @@ impl Text40x25 {
 
     /// Sets the graphics device to `VideoMode::Mode40x25`.
     pub fn set_mode(&self) {
-        VGA.lock().set_video_mode(VideoMode::Mode40x25);
+        let mut vga = VGA.lock();
+        vga.set_video_mode(VideoMode::Mode40x25);
+
+        // Some bios mess up the palette when switching modes,
+        // so explicitly set it.
+        vga.load_palette(&DEFAULT_PALETTE);
     }
 
     /// Returns the start of the `FrameBuffer` as `*mut ScreenCharacter`

src/writers/text_40x50.rs

@@ -1,6 +1,6 @@
 use super::ScreenCharacter;
 use crate::{
-    colors::{Color16Bit, TextModeColor},
+    colors::{Color16Bit, TextModeColor, DEFAULT_PALETTE},
     vga::{Vga, VideoMode, VGA},
 };
 use spinning_top::SpinlockGuard;
@@ -66,7 +66,12 @@ impl Text40x50 {
 
     /// Sets the graphics device to `VideoMode::Mode40x50`.
     pub fn set_mode(&self) {
-        VGA.lock().set_video_mode(VideoMode::Mode40x50);
+        let mut vga = VGA.lock();
+        vga.set_video_mode(VideoMode::Mode40x50);
+
+        // Some bios mess up the palette when switching modes,
+        // so explicitly set it.
+        vga.load_palette(&DEFAULT_PALETTE);
     }
 
     /// Returns the start of the `FrameBuffer` as `*mut ScreenCharacter`

src/writers/text_80x25.rs

@@ -1,6 +1,6 @@
 use super::ScreenCharacter;
 use crate::{
-    colors::{Color16Bit, TextModeColor},
+    colors::{Color16Bit, TextModeColor, DEFAULT_PALETTE},
     vga::{Vga, VideoMode, VGA},
 };
 use spinning_top::SpinlockGuard;
@@ -66,7 +66,12 @@ impl Text80x25 {
 
     /// Sets the graphics device to `VideoMode::Mode80x25`.
     pub fn set_mode(&self) {
-        VGA.lock().set_video_mode(VideoMode::Mode80x25);
+        let mut vga = VGA.lock();
+        vga.set_video_mode(VideoMode::Mode80x25);
+
+        // Some bios mess up the palette when switching modes,
+        // so explicitly set it.
+        vga.load_palette(&DEFAULT_PALETTE);
     }
 
     /// Returns the start of the `FrameBuffer` as `*mut ScreenCharacter`

testing/tests/vga.rs

@@ -7,8 +7,9 @@
 use core::panic::PanicInfo;
 use testing::{gdt, interrupts, serial_print, serial_println};
 use vga::{
-    Vga, VgaConfiguration, VideoMode, MODE_40X25_CONFIGURATION, MODE_40X50_CONFIGURATION,
+    Vga, VgaConfiguration, VideoMode, DEFAULT_PALETTE, MODE_40X25_CONFIGURATION,
-    MODE_640X480X16_CONFIGURATION, MODE_80X25_CONFIGURATION, VGA,
+    MODE_40X50_CONFIGURATION, MODE_640X480X16_CONFIGURATION, MODE_80X25_CONFIGURATION,
+    PALETTE_SIZE, VGA,
 };
 
 #[no_mangle] // don't mangle the name of this function
@@ -75,6 +76,22 @@ fn set_mode_640x480x16() {
     serial_println!("[ok]");
 }
 
+#[test_case]
+fn load_palette() {
+    serial_print!("load palette... ");
+
+    let mut palette = [0u8; PALETTE_SIZE];
+    let mut vga = VGA.lock();
+    vga.load_palette(&DEFAULT_PALETTE);
+    vga.read_palette(&mut palette);
+
+    for i in 0..PALETTE_SIZE {
+        assert_eq!(palette[i], DEFAULT_PALETTE[i]);
+    }
+
+    serial_println!("[ok]");
+}
+
 fn check_registers(vga: &mut Vga, configuration: &VgaConfiguration) {
     let emulation_mode = vga.get_emulation_mode();
     assert_eq!(vga.read_msr(), configuration.miscellaneous_output);