Add read operation to /dev/vga/palette

Author: vinc

src/sys/vga/mod.rs

@@ -27,6 +27,7 @@ const ATTR_READ_REG:           u16 = 0x3C1;
 const MISC_WRITE_REG:          u16 = 0x3C2;
 const SEQUENCER_ADDR_REG:      u16 = 0x3C4;
 const SEQUENCER_DATA_REG:      u16 = 0x3C5;
+const DAC_ADDR_READ_MODE_REG:  u16 = 0x3C7;
 const DAC_ADDR_WRITE_MODE_REG: u16 = 0x3C8;
 const DAC_DATA_REG:            u16 = 0x3C9;
 const GRAPHICS_ADDR_REG:       u16 = 0x3CE;
@@ -75,11 +76,6 @@ struct ScreenBuffer {
     chars: [[ScreenChar; SCREEN_WIDTH]; SCREEN_HEIGHT],
 }
 
-// Convert 8-bit to 6-bit color
-fn vga_color(color: u8) -> u8 {
-    color >> 2
-}
-
 // TODO: Remove this
 fn parse_palette(palette: &str) -> Result<(usize, u8, u8, u8), ParseIntError> {
     debug_assert!(palette.len() == 8);

src/sys/vga/palette.rs

@@ -42,12 +42,30 @@ impl Palette {
         palette
     }
 
+    pub fn get() -> Self {
+        let mut palette = Palette::new();
+        for i in 0..256 {
+            palette.colors[i] = get_palette(i);
+        }
+        palette
+    }
+
     pub fn set(&self) {
         for (i, (r, g, b)) in self.colors.iter().enumerate() {
             set_palette(i, *r, *g, *b);
         }
     }
 
+    pub fn to_bytes(&self) -> [u8; 256 * 3] {
+        let mut buf = [0; 256 * 3];
+        for (i, (r, g, b)) in self.colors.iter().enumerate() {
+            buf[i * 3 + 0] = *r;
+            buf[i * 3 + 1] = *g;
+            buf[i * 3 + 2] = *b;
+        }
+        buf
+    }
+
     pub fn size() -> usize {
         256 * 3
     }
@@ -70,8 +88,13 @@ impl TryFrom<&[u8]> for Palette {
 }
 
 impl FileIO for VgaPalette {
-    fn read(&mut self, _buf: &mut [u8]) -> Result<usize, ()> {
-        Err(()) // TODO
+    fn read(&mut self, buf: &mut [u8]) -> Result<usize, ()> {
+        let res = Palette::get().to_bytes();
+        if buf.len() < res.len() {
+            return Err(());
+        }
+        buf.clone_from_slice(&res);
+        Ok(res.len())
     }
 
     fn write(&mut self, buf: &[u8]) -> Result<usize, ()> {
@@ -84,14 +107,22 @@ impl FileIO for VgaPalette {
 
     fn poll(&mut self, event: IO) -> bool {
         match event {
-            IO::Read => false, // TODO
-            IO::Write => true, // TODO
+            IO::Read => true,
+            IO::Write => true,
         }
     }
 }
 
-pub fn set_palette(i: usize, r: u8, g: u8, b: u8) {
+// TODO: Rename to `write_palette_index`
+fn set_palette(i: usize, r: u8, g: u8, b: u8) {
     interrupts::without_interrupts(||
         WRITER.lock().set_palette(i, r, g, b)
     )
 }
+
+// TODO: Rename to `read_palette_index`
+fn get_palette(i: usize) -> (u8, u8, u8) {
+    interrupts::without_interrupts(||
+        WRITER.lock().palette(i)
+    )
+}

src/sys/vga/writer.rs

@@ -272,9 +272,21 @@ impl Writer {
         let mut data: Port<u8> = Port::new(DAC_DATA_REG);
         unsafe {
             addr.write(i as u8);
-            data.write(vga_color(r));
-            data.write(vga_color(g));
-            data.write(vga_color(b));
+            data.write(r >> 2); // Convert 8-bit to 6-bit color
+            data.write(g >> 2);
+            data.write(b >> 2);
+        }
+    }
+
+    pub fn palette(&mut self, i: usize) -> (u8, u8, u8) {
+        let mut addr: Port<u8> = Port::new(DAC_ADDR_READ_MODE_REG);
+        let mut data: Port<u8> = Port::new(DAC_DATA_REG);
+        unsafe {
+            addr.write(i as u8);
+            let r = data.read() << 2; // Convert 6-bit to 8-bit color
+            let g = data.read() << 2;
+            let b = data.read() << 2;
+            (r, g, b)
         }
     }