Add comments to explain CGA ports better

10 files changed, 194 insertions, 159 deletions

diff --git a/drivers/cga.cc b/drivers/cga.cc
new file mode 100644
index 0000000..79facee
--- /dev/null
+++ b/drivers/cga.cc
@@ -0,0 +1,111 @@
+#include "cga.h"
+#include <string.h>
+
+static_assert(sizeof(CGA::Entry) == 2);
+
+/* cga registers, see https://www.lowlevel.eu/wiki/Color_Graphics_Adapter */
+constexpr uint8_t cursor_start = 10;   // 0xa
+constexpr uint8_t cursor_end = 11;     // 0xb
+constexpr uint8_t cursor_addr_h = 14;  // 0xe
+constexpr uint8_t cursor_addr_l = 15;  // 0xf
+
+/* cursor format
+ * register | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
+ *   start  |   | e | t |     scanline      |
+ *   end    |           |     scanline      |
+ * e = enable; t = timing
+ *  e t | effect
+ *  0 0 | no blinking
+ *  0 1 | hide cursor
+ *  1 0 | blink normally
+ *  1 1 | blink fast
+ */
+constexpr uint8_t cursor_hide = 0b00100000;
+
+CGA::CGA(Colour fg, Colour bg, uint32_t address) : colour_fg(fg), colour_bg(bg) {
+  buffer = reinterpret_cast<Entry*>(address);
+
+  // clear buffer
+  for (size_t y = 0; y < max_rows; y++) {
+    for (size_t x = 0; x < max_columns; x++) {
+      const size_t index = y * max_columns + x;
+      buffer[index].c = ' ';
+      buffer[index].fg = colour_fg;
+      buffer[index].bg = colour_bg;
+    }
+  }
+
+  enable_cursor(14, 15);
+  update_cursor();
+}
+
+void CGA::set_colour(Colour fg, Colour bg) {
+  colour_fg = fg;
+  colour_bg = bg;
+  for (size_t y = 0; y < max_rows; y++) {
+    for (size_t x = 0; x < max_columns; x++) {
+      const size_t index = y * max_columns + x;
+      buffer[index].fg = colour_fg;
+      buffer[index].bg = colour_bg;
+    }
+  }
+}
+
+void CGA::enable_cursor(uint8_t start, uint8_t end) {
+  p_idx.write(cursor_start);
+  p_dat.write((p_dat.read() & 0xc0) | start);
+
+  p_idx.write(cursor_end);
+  p_dat.write((p_dat.read() & 0xe0) | end);
+}
+void CGA::disable_cursor() {
+  p_idx.write(cursor_start);
+  p_dat.write(cursor_hide);
+}
+void CGA::update_cursor() {
+  const uint16_t pos = row * max_columns + column;
+
+  p_idx.write(cursor_addr_l);
+  p_dat.write(static_cast<uint8_t>(pos & 0xff));
+
+  p_idx.write(cursor_addr_h);
+  p_dat.write(static_cast<uint8_t>((pos >> 8) & 0xff));
+}
+
+void CGA::write(char c) {
+  switch (c) {
+    case '\n':
+      column = 0;
+      ++row;
+      break;
+    default: {
+      const size_t index = row * max_columns + column;
+      buffer[index].c = c;
+      ++column;
+    }
+  }
+
+  if (column == max_columns) {
+    column = 0;
+    ++row;
+  }
+
+  if (row == max_rows) {
+    // scroll up - move rows 1~25 up by one
+    for (size_t y = 1; y < max_rows; y++) {
+      const auto prev_y = y - 1;
+      for (size_t x = 0; x < max_columns; ++x) {
+        const auto prev = prev_y * max_columns + x;
+        const auto idx = y * max_columns + x;
+        buffer[prev] = buffer[idx];
+      }
+    }
+    --row;
+  }
+}
+
+void CGA::write(ViewIterator& iter) {
+  while (iter) {
+    write(iter.next());
+  }
+}
diff --git a/drivers/cga.h b/drivers/cga.h
new file mode 100644
index 0000000..f0ca412
--- /dev/null
+++ b/drivers/cga.h
@@ -0,0 +1,69 @@
+#pragma once
+#include <stdlib.h>
+#include "ports.h"
+
+/*
+ * CGA (Colour Graphics Adapter)
+ *
+ * useful links:
+ * https://www.seasip.info/VintagePC/cga.html
+ * https://www.lowlevel.eu/wiki/Color_Graphics_Adapter
+ *
+ * TODO: switching between modes
+ * TODO: cursor styling
+ */
+
+class CGA : public Console {
+public:
+  /* Hardware text mode colour constants. */
+  enum Colour : uint8_t {
+    CGA_COLOR_BLACK = 0,
+    CGA_COLOR_BLUE = 1,
+    CGA_COLOR_GREEN = 2,
+    CGA_COLOR_CYAN = 3,
+    CGA_COLOR_RED = 4,
+    CGA_COLOR_MAGENTA = 5,
+    CGA_COLOR_BROWN = 6,
+    CGA_COLOR_LIGHT_GREY = 7,
+    CGA_COLOR_DARK_GREY = 8,
+    CGA_COLOR_LIGHT_BLUE = 9,
+    CGA_COLOR_LIGHT_GREEN = 10,
+    CGA_COLOR_LIGHT_CYAN = 11,
+    CGA_COLOR_LIGHT_RED = 12,
+    CGA_COLOR_LIGHT_MAGENTA = 13,
+    CGA_COLOR_LIGHT_BROWN = 14,
+    CGA_COLOR_WHITE = 15,
+  };
+
+  CGA(Colour fg = CGA_COLOR_BLACK, Colour bg = CGA_COLOR_LIGHT_GREY, uint32_t address = 0xB8000);
+  ~CGA() = default;
+
+  void set_colour(Colour fg, Colour bg);
+
+  void enable_cursor(uint8_t start, uint8_t end);
+  void disable_cursor();
+  void update_cursor() override;
+
+  void write(char c) override;
+  void write(ViewIterator& iter) override;
+
+
+  struct Entry {
+    char c;
+    Colour fg : 4;
+    Colour bg : 4;
+  } __attribute((packed));
+
+private:
+  const size_t max_columns = 80, max_rows = 25;
+  size_t column = 0, row = 0;
+
+  Colour colour_fg;
+  Colour colour_bg;
+
+  Entry* buffer;
+
+  // ports
+  cga_idx_port p_idx;
+  cga_dat_port p_dat;
+};
diff --git a/drivers/makefile b/drivers/makefile
new file mode 100644
index 0000000..b76f7c5
--- /dev/null
+++ b/drivers/makefile
@@ -0,0 +1 @@
+CXX_OBJ += drivers/cga.o
diff --git a/src/ports.h b/drivers/ports.h
index 0371bcc..338c3b8 100644
--- a/src/ports.h
+++ b/drivers/ports.h
@@ -39,5 +39,9 @@ public:
   }
 };
 
-typedef Port<0x3d4, uint8_t> vga_horizontal_total;
-typedef Port<0x3d5, uint8_t> vga_horizontal_display_enable_end;
+/* Ports 0x3d0 to 0x3df are reserved for CGA; each port is 1 byte wide */
+typedef Port<0x3d4, uint8_t> cga_idx_port;
+typedef Port<0x3d5, uint8_t> cga_dat_port;
+// 0x3d8 : mode select register
+// 0x3d8 : color control register
+// 0x3da : status register
diff --git a/makefile b/makefile
index f65e699..ccb2b1a 100644
--- a/makefile
+++ b/makefile
@@ -1,8 +1,10 @@
 include toolchain.makefile
 OBJ_DIR := build
 
-include src/makefile
 include libk/makefile
+include src/makefile
+include drivers/makefile
+
 AS_OBJ := $(addprefix $(OBJ_DIR)/, $(AS_OBJ))
 CXX_OBJ := $(addprefix $(OBJ_DIR)/, $(CXX_OBJ))
 CXX_DEP = $(CXX_OBJ:%o=%.d)
@@ -29,7 +31,7 @@ $(CXX_OBJ) $(CXX_TEST_OBJ): $(OBJ_DIR)/%.o : %.cc
 	@$(CXX) -target $(TARGET) $(CXX_FLAGS) $(CXX_INCLUDE) $(CXX_SYSTEM_INCLUDE) -MMD -c $^ -o $@
 
 clean:
-	rm -rf $(AS_OBJ) $(CXX_OBJ) $(CXX_DEP) $(CXX_TEST_OBJ) glitch.elf isodir
+	@rm -rf $(AS_OBJ) $(CXX_OBJ) $(CXX_DEP) $(CXX_TEST_OBJ) glitch.elf isodir
 
 # testing
 test: $(CXX_TEST_OBJ) check-grub
diff --git a/src/kernel.cc b/src/kernel.cc
index 4569107..4c17969 100644
--- a/src/kernel.cc
+++ b/src/kernel.cc
@@ -10,15 +10,15 @@
 
 #include <stdlib.h>
 #include <types.h>
+#include "cga.h"
 #include "gdt.h"
-#include "vga.h"
 
 extern "C" {
 void dump_multiboot(uint32_t mb_magic, uint32_t mb_addr);
 void dump_gdt();
 
 void kernel_main([[maybe_unused]] uint32_t mb_magic, [[maybe_unused]] uint32_t mb_addr) {
-  VGA terminal;
+  CGA terminal;
   Console::set(&terminal);
 
   printk("Hello, kernel World!\n");
diff --git a/src/makefile b/src/makefile
index 25c58be..8214d03 100644
--- a/src/makefile
+++ b/src/makefile
@@ -4,6 +4,5 @@ CXX_OBJ += src/kernel.o \
 	   src/kernel/dump_gdt.o \
 	   src/kernel/dump_multiboot.o \
 	   src/memory.o \
-	   src/vga.o \
 	   src/gdt.o \
 	   src/gdt/segmentdescriptor.o
diff --git a/src/vga.cc b/src/vga.cc
deleted file mode 100644
index 66a6b3a..0000000
--- a/src/vga.cc
+++ /dev/null
@@ -1,92 +0,0 @@
-#include "vga.h"
-#include <string.h>
-
-static_assert(sizeof(VGA::Entry) == 2);
-
-VGA::VGA(vga_color fg, vga_color bg, uint32_t address) : color_fg(fg), color_bg(bg) {
-  buffer = reinterpret_cast<Entry*>(address);
-
-  // clear buffer
-  for (size_t y = 0; y < max_rows; y++) {
-    for (size_t x = 0; x < max_columns; x++) {
-      const size_t index = y * max_columns + x;
-      buffer[index].c = ' ';
-      buffer[index].fg = color_fg;
-      buffer[index].bg = color_bg;
-    }
-  }
-
-  enable_cursor(14, 15);
-  update_cursor();
-}
-
-void VGA::set_color(vga_color fg, vga_color bg) {
-  color_fg = fg;
-  color_bg = bg;
-  for (size_t y = 0; y < max_rows; y++) {
-    for (size_t x = 0; x < max_columns; x++) {
-      const size_t index = y * max_columns + x;
-      buffer[index].fg = color_fg;
-      buffer[index].bg = color_bg;
-    }
-  }
-}
-
-void VGA::enable_cursor(uint8_t start, uint8_t end) {
-  p_3d4.write(0x0a);
-  p_3d5.write((p_3d5.read() & 0xc0) | start);
-
-  p_3d4.write(0x0b);
-  p_3d5.write((p_3d5.read() & 0xe0) | end);
-}
-void VGA::disable_cursor() {
-  p_3d4.write(0x0a);
-  p_3d5.write(0x20);
-}
-void VGA::update_cursor() {
-  const uint16_t pos = row * max_columns + column;
-
-  p_3d4.write(0x0f);
-  p_3d5.write(static_cast<uint8_t>(pos & 0xff));
-
-  p_3d4.write(0x0e);
-  p_3d5.write(static_cast<uint8_t>((pos >> 8) & 0xff));
-}
-
-void VGA::write(char c) {
-  switch (c) {
-    case '\n':
-      column = 0;
-      ++row;
-      break;
-    default: {
-      const size_t index = row * max_columns + column;
-      buffer[index].c = c;
-      ++column;
-    }
-  }
-
-  if (column == max_columns) {
-    column = 0;
-    ++row;
-  }
-
-  if (row == max_rows) {
-    // scroll up - move rows 1~25 up by one
-    for (size_t y = 1; y < max_rows; y++) {
-      const auto prev_y = y - 1;
-      for (size_t x = 0; x < max_columns; ++x) {
-        const auto prev = prev_y * max_columns + x;
-        const auto idx = y * max_columns + x;
-        buffer[prev] = buffer[idx];
-      }
-    }
-    --row;
-  }
-}
-
-void VGA::write(ViewIterator& iter) {
-  while (iter) {
-    write(iter.next());
-  }
-}
diff --git a/src/vga.h b/src/vga.h
deleted file mode 100644
index 7a8c755..0000000
--- a/src/vga.h
+++ /dev/null
@@ -1,59 +0,0 @@
-#pragma once
-#include <stdlib.h>
-#include "ports.h"
-
-class VGA : public Console {
-public:
-  /* Hardware text mode color constants. */
-  enum vga_color : uint8_t {
-    VGA_COLOR_BLACK = 0,
-    VGA_COLOR_BLUE = 1,
-    VGA_COLOR_GREEN = 2,
-    VGA_COLOR_CYAN = 3,
-    VGA_COLOR_RED = 4,
-    VGA_COLOR_MAGENTA = 5,
-    VGA_COLOR_BROWN = 6,
-    VGA_COLOR_LIGHT_GREY = 7,
-    VGA_COLOR_DARK_GREY = 8,
-    VGA_COLOR_LIGHT_BLUE = 9,
-    VGA_COLOR_LIGHT_GREEN = 10,
-    VGA_COLOR_LIGHT_CYAN = 11,
-    VGA_COLOR_LIGHT_RED = 12,
-    VGA_COLOR_LIGHT_MAGENTA = 13,
-    VGA_COLOR_LIGHT_BROWN = 14,
-    VGA_COLOR_WHITE = 15,
-  };
-
-  VGA(vga_color fg = VGA_COLOR_BLACK, vga_color bg = VGA_COLOR_LIGHT_GREY, uint32_t address = 0xB8000);
-  ~VGA() = default;
-
-  void set_color(vga_color fg, vga_color bg);
-
-  void enable_cursor(uint8_t start, uint8_t end);
-  void disable_cursor();
-  void update_cursor() override;
-
-  void write(char c) override;
-  void write(ViewIterator& iter) override;
-
-
-  struct Entry {
-    char c;
-    vga_color fg : 4;
-    vga_color bg : 4;
-  } __attribute((packed));
-
-private:
-  const size_t max_columns = 80, max_rows = 25;
-  size_t column = 0, row = 0;
-
-  vga_color color_fg;
-  vga_color color_bg;
-
-  Entry* buffer;
-
-  // ports
-  vga_horizontal_total p_3d4;
-  vga_horizontal_display_enable_end p_3d5;
-};
-
diff --git a/toolchain.makefile b/toolchain.makefile
index fe916e4..9dc5b17 100644
--- a/toolchain.makefile
+++ b/toolchain.makefile
@@ -15,7 +15,7 @@ CXX_FLAGS   := -std=c++20 -ffreestanding -nostdlib -nostdinc -nostdinc++ \
 	       -Wnon-virtual-dtor \
 	       -Wold-style-cast -Wconversion \
 	       -Wconsumed
-CXX_INCLUDE := $(CURDIR)/libk
+CXX_INCLUDE := $(CURDIR)/libk $(CURDIR)/drivers
 CXX_SYSTEM_INCLUDE := $(CURDIR)/grub
 
 #