feat(bus): implement Palette RAM and DISPSTAT

src/bus/io.zig

@@ -6,37 +6,43 @@ const Bit = bitfield.Bit;
 
 pub const Io = struct {
     dispcnt: Dispcnt,
+    dispstat: Dispstat,
 
     pub fn init() @This() {
         return .{
-            .dispcnt = .{ .val = 0x0000_0000 },
+            .dispcnt = .{ .raw = 0x0000_0000 },
+            .dispstat = .{ .raw = 0x0000_0000 },
         };
     }
 
     pub fn read32(self: *const @This(), addr: u32) u32 {
         return switch (addr) {
-            0x0400_0000 => @as(u32, self.dispcnt.val),
+            0x0400_0000 => @as(u32, self.dispcnt.raw),
+            0x0400_0004 => @as(u32, self.dispstat.raw),
             else => std.debug.panic("[I/O:32] tried to read from {X:}", .{addr}),
         };
     }
 
     pub fn read16(self: *const @This(), addr: u32) u16 {
         return switch (addr) {
-            0x0400_0000 => self.dispcnt.val,
+            0x0400_0000 => self.dispcnt.raw,
+            0x0400_0004 => self.dispstat.raw,
             else => std.debug.panic("[I/O:16] tried to read from {X:}", .{addr}),
         };
     }
 
     pub fn write16(self: *@This(), addr: u32, halfword: u16) void {
         switch (addr) {
-            0x0400_0000 => self.dispcnt.val = halfword,
+            0x0400_0000 => self.dispcnt.raw = halfword,
+            0x0400_0004 => self.dispstat.raw = halfword,
             else => std.debug.panic("[I/O:16] tried to write 0x{X:} to 0x{X:}", .{ halfword, addr }),
         }
     }
 
     pub fn read8(self: *const @This(), addr: u32) u8 {
         return switch (addr) {
-            0x0400_0000 => @truncate(u8, self.dispcnt.val),
+            0x0400_0000 => @truncate(u8, self.dispcnt.raw),
+            0x0400_0004 => @truncate(u8, self.dispstat.raw),
             else => std.debug.panic("[I/O:8] tried to read from {X:}", .{addr}),
         };
     }
@@ -45,12 +51,23 @@ pub const Io = struct {
 const Dispcnt = extern union {
     bg_mode: Bitfield(u16, 0, 3),
     frame_select: Bit(u16, 4),
-    hblank_interval_free: Bit(u16, 5),
+    hblank_interraw_free: Bit(u16, 5),
     obj_mapping: Bit(u16, 6),
     forced_blank: Bit(u16, 7),
     bg_enable: Bitfield(u16, 8, 4),
     obj_enable: Bit(u16, 12),
     win_enable: Bitfield(u16, 13, 2),
     obj_win_enable: Bit(u16, 15),
-    val: u16,
+    raw: u16,
+};
+
+const Dispstat = extern union {
+    vblank: Bit(u16, 0),
+    hblank: Bit(u16, 1),
+    vcount: Bit(u16, 2),
+    vblank_irq: Bit(u16, 3),
+    hblank_irq: Bit(u16, 4),
+    vcount_irq: Bit(u16, 5),
+    vcount_setting: Bitfield(u16, 8, 7),
+    raw: u16,
 };