printing debug messages to serial only

src/console.zig

@@ -120,3 +120,22 @@ pub const Console = struct {
         while (x < self.fb.width) : (x += 1) dst[x] = src[x];
     }
 };
+
+pub const SerialConsole = struct {
+    /// Serial-only output: goes to the machine-readable log but *not* the framebuffer,
+/// so debug and test detail stays out of the on-screen console. These are free
+/// functions, not `Console` methods, because serial has no dependency on the
+/// framebuffer — they work even before `con` is initialised.
+pub fn debugWrite(bytes: []const u8) void {
+        arch.serialWrite(bytes);
+    }
+
+    /// Formatted serial-only output, e.g. `debugPrint("x={d}\n", .{x})`. Truncates
+    /// past 256 bytes, like `Console.print`.
+pub fn debugPrint(comptime fmt: []const u8, args: anytype) void {
+        var buf: [256]u8 = undefined;
+        debugWrite(std.fmt.bufPrint(&buf, fmt, args) catch return);
+    }
+
+};
+