From 28309db7b9c5891cae61f5cf589118704105d1f4 Mon Sep 17 00:00:00 2001
From: Mathieu Maret <mathieu.maret@gmail.com>
Date: Thu, 11 Apr 2019 22:32:50 +0200
Subject: [PATCH] Add printf for debug: pr_devel

Taken from linux kernel
---
 drivers/vga.h | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/drivers/vga.h b/drivers/vga.h
index fd041fc..5c90649 100644
--- a/drivers/vga.h
+++ b/drivers/vga.h
@@ -1,5 +1,6 @@
 #pragma once
 #include "stdarg.h"
+#include "stdint.h"
 
 // https://wiki.osdev.org/Text_UI
 #define BLACK   0x00
@@ -16,6 +17,10 @@
 #define VGA_WIDTH  80
 #define VGA_HEIGHT 25
 
+#ifndef pr_fmt
+#define pr_fmt(fmt) fmt
+#endif
+
 void vprintf(const char *format, va_list ap);
 void printf(const char *format, ...);
 int VGASetup(uint bgColor, uint color);
@@ -31,3 +36,22 @@ void vgaScrollUp(void);
 void cursorEnable(uint8_t cursor_start, uint8_t cursor_end);
 void cursorDisable(void);
 void cursorMove(int x, int y);
+
+/*
+ * Dummy printk for disabled debugging statements to use whilst maintaining
+ * gcc's format checking.
+ */
+#define no_printf(fmt, ...)				\
+({							\
+	if (0)						\
+		printf(fmt, ##__VA_ARGS__);		\
+	0;						\
+})
+
+#ifdef DEBUG
+#define pr_devel(fmt, ...) \
+	printf(pr_fmt(fmt), ##__VA_ARGS__)
+#else
+#define pr_devel(fmt, ...) \
+	no_printf(pr_fmt(fmt), ##__VA_ARGS__)
+#endif