From ed16669fb8629fde0593bd4b8dc266a697af6245 Mon Sep 17 00:00:00 2001
From: Carlos Maiolino <cem@toxiclabs.cc>
Date: Fri, 25 Jul 2025 08:20:12 +0200
Subject: Add VGA text mode driver

Add driver to deal with VGA text mode.

Also adds a simple vprintl function while I don't implement a print
library.

Signed-off-by: Carlos Maiolino <cem@toxiclabs.cc>
---
 src/include/vga.h | 25 +++++++++++++++++
 src/vga.c         | 81 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 106 insertions(+)
 create mode 100644 src/include/vga.h
 create mode 100644 src/vga.c

(limited to 'src')

diff --git a/src/include/vga.h b/src/include/vga.h
new file mode 100644
index 0000000..7aaa210
--- /dev/null
+++ b/src/include/vga.h
@@ -0,0 +1,25 @@
+#ifndef VGA_H
+#define VGA_H
+#include <stddef.h>
+
+#define VGA_ADDRESS 0xb8000
+#define VGA_WIDTH 80
+#define VGA_HEIGHT 20
+
+struct vga_display {
+	uint16_t	*buf;
+	uint16_t	color;
+	size_t		row;
+	size_t		col;
+};
+
+extern struct vga_display display;
+
+void vga_put_char(size_t row, size_t col, char c, uint16_t color);
+void vga_write_char(char c);
+void vprintl(char *str);
+
+void init_display(uint16_t color);
+
+
+#endif /* VGA_H */
diff --git a/src/vga.c b/src/vga.c
new file mode 100644
index 0000000..52109c6
--- /dev/null
+++ b/src/vga.c
@@ -0,0 +1,81 @@
+#include <stdint.h>
+#include <stddef.h>
+#include <vga.h>
+#include "lib/string.h"
+
+struct vga_display display;
+
+void
+vga_set_color(uint16_t c)
+{
+	display.color = c;
+}
+
+void
+vga_set_pos(size_t r, size_t c)
+{
+	display.row = r;
+	display.col = c;
+}
+
+static uint16_t
+vga_build_char(char c, char color)
+{
+	return (uint16_t)((color << 8) | c);
+}
+
+void
+vga_put_char(size_t row, size_t col, char c, uint16_t color)
+{
+	size_t pos = (VGA_WIDTH * row) + col;
+	display.buf[pos] = vga_build_char(c, color);
+}
+
+void
+vga_write_char(char c)
+{
+	switch (c) {
+	case '\n':
+		vga_set_pos(++display.row, 0);
+		break;
+	default:
+		vga_put_char(display.row, display.col, c, display.color);
+		display.col++;
+	}
+
+
+	if (display.col == VGA_WIDTH)
+		vga_set_pos(++display.row, 0);
+}
+
+void
+vprintl(char *str)
+{
+	int i = 0;
+	size_t len = strlen(str);
+
+	for (i = 0; i <= len; i++) {
+		vga_write_char(str[i]);
+	}
+}
+
+static void
+clean_display(void)
+{
+	int row, col;
+
+	for (row = 0; row < VGA_HEIGHT; row++)
+		for (col = 0; col < VGA_WIDTH; col++)
+			vga_put_char(row, col, ' ', 0);
+}
+
+void
+init_display(uint16_t color)
+{
+	display.buf = (uint16_t *)VGA_ADDRESS;
+	vga_set_pos(0, 0);
+	clean_display();
+	vga_set_color(color);
+	vga_set_pos(0, 0);
+}
+
-- 
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