From fd5a3001e12a341fd23cedcf63a37b399b52e0d1 Mon Sep 17 00:00:00 2001
From: Joursoir <chat@joursoir.net>
Date: Thu, 5 Aug 2021 14:44:54 +0000
Subject: video-vga: add routines for vga

---
 kernel/video-vga.c | 98 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 kernel/video-vga.h | 36 ++++++++++++++++++++
 2 files changed, 134 insertions(+)
 create mode 100644 kernel/video-vga.c
 create mode 100644 kernel/video-vga.h

diff --git a/kernel/video-vga.c b/kernel/video-vga.c
new file mode 100644
index 0000000..4a7a14c
--- /dev/null
+++ b/kernel/video-vga.c
@@ -0,0 +1,98 @@
+#include "video-vga.h"
+#include "string.h"
+#include "i386.h"
+
+#define VGA_BASE 0xB8000
+#define CRTC_PORT 0x3D4
+
+#define VGA_WIDTH 80
+#define VGA_HEIGHT 25
+
+static size_t vga_row, vga_column;
+static uint8_t vga_color;
+static uint16_t *vga_buffer;
+
+uint8_t vga_entry_color(enum vga_colors fg, enum vga_colors bg)
+{
+	return fg | bg << 4;
+}
+
+uint16_t vga_entry(uint8_t uc, uint8_t color)
+{
+	return (uint16_t) uc | (uint16_t) color << 8;
+}
+
+void vga_init(void)
+{
+	size_t x, y;
+	size_t vga_char;
+	vga_row = 0, vga_column = 0;
+	vga_color = vga_entry_color(VGA_COLOR_LIGHT_GREY, VGA_COLOR_BLACK);
+	vga_char = vga_entry(' ', vga_color);
+	vga_buffer = (uint16_t *) VGA_BASE;
+	for(y = 0; y < VGA_HEIGHT; y++) {
+		for(x = 0; x < VGA_WIDTH; x++) {
+			const size_t index = y * VGA_WIDTH + x;
+			vga_buffer[index] = vga_char;
+		}
+	}
+}
+
+void vga_setcolor(uint8_t color)
+{
+	vga_color = color;
+}
+
+void vga_scroll(size_t lines)
+{
+	size_t count = (VGA_HEIGHT - lines) * VGA_WIDTH;
+	size_t vga_char = vga_entry(' ', vga_color);
+
+	memmove(vga_buffer, vga_buffer + VGA_WIDTH * lines, count * 2);
+	for(; count < (vga_row + 1) * VGA_WIDTH; count++)
+		vga_buffer[count] = vga_char;
+}
+
+void vga_putchar(char c)
+{
+	uint16_t pos;
+	if(c == '\n') {
+		vga_column = 0;
+		if(++vga_row >= VGA_HEIGHT) {
+			vga_scroll(1);
+			vga_row--;
+		}	
+	}
+	else {
+		const size_t index = vga_row * VGA_WIDTH + vga_column;
+		vga_buffer[index] = vga_entry(c, vga_color);
+
+		if(++vga_column >= VGA_WIDTH) {
+			vga_column = 0;
+			if(++vga_row >= VGA_HEIGHT) {
+				vga_scroll(1);
+				vga_row--;
+			}
+		}
+	}
+
+	/* Update cursor position */
+	pos = vga_row * VGA_WIDTH + vga_column;
+	outb(CRTC_PORT, 0x0E);
+	outb(CRTC_PORT+1, (uint8_t) ((pos >> 8) & 0xFF));
+	outb(CRTC_PORT, 0x0F);
+	outb(CRTC_PORT+1, (uint8_t) (pos & 0xFF));
+}
+
+
+void vga_write(const char *str, size_t size)
+{
+	size_t i;
+	for(i = 0; i < size; i++)
+		vga_putchar(str[i]);
+}
+
+void vga_print(const char *str)
+{
+	vga_write(str, strlen(str));
+}
diff --git a/kernel/video-vga.h b/kernel/video-vga.h
new file mode 100644
index 0000000..ddcfc31
--- /dev/null
+++ b/kernel/video-vga.h
@@ -0,0 +1,36 @@
+#ifndef KERNEL_VIDEO_VGA
+#define KERNEL_VIDEO_VGA
+
+#include <stddef.h>
+#include <stdint.h>
+
+/* Hardware text mode color constants. */
+enum vga_colors {
+	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
+};
+
+uint8_t vga_entry_color(enum vga_colors fg, enum vga_colors bg);
+uint16_t vga_entry(uint8_t uc, uint8_t color);
+void vga_init(void);
+void vga_setcolor(uint8_t color);
+void vga_scroll(size_t lines);
+void vga_putchar(char c);
+void vga_write(const char *str, size_t size);
+void vga_print(const char *str);
+
+#endif /* KERNEL_VIDEO_VGA */
-- 
cgit v1.2.3-18-g5258