RockOS/kernel/drivers/vga/vga.c

#include <stddef.h>
#include <stdint.h>

#include <lib/stream.h>

#include <drivers/vga/vga.h>

#include <common.h>

static uint32_t framebuffer_address;
static uint32_t framebuffer_width;
static uint32_t framebuffer_height;
static uint32_t framebuffer_total_pixels;
static uint32_t framebuffer_pitch;
static uint32_t framebuffer_bpp;

enum vga_color {
	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,
};

void vga_init(
	uint32_t fb_vaddr,
	uint32_t fb_width,
	uint32_t fb_height,
	uint32_t fb_pitch,
	uint8_t fb_bpp
) {
	framebuffer_address = fb_vaddr;
	framebuffer_width = fb_width;
	framebuffer_height = fb_height;
	framebuffer_pitch = fb_pitch;
	framebuffer_bpp = fb_bpp;

	framebuffer_total_pixels = framebuffer_width * framebuffer_height;

	vga_clear_scrn(0xFFFFFFFF);
}

void vga_clear_scrn(uint32_t color) {
	if (framebuffer_address == 0) return;

	// Completely ignore the framebuffer address for a split second.
    // Let's force raw ASCII text into the legacy VGA text console area.
    uint16_t* text_mode_buffer = (uint16_t*)0xB8000;
    
    // Fill the screen with 'A' characters on a red background
    for (int i = 0; i < 80 * 25; i++) {
        text_mode_buffer[i] = (0x4F << 8) | 'A'; 
    }
}

void vga_putchar(char c) {
	if (c == '\n') {
		return;
	}

	if (c == '\t') {
		for (int i = 0; i < 4; i++) {
			vga_putchar(' ');
		}
		return;
	}
}

uint32_t vga_seek(vfs_node_t* node, uint32_t offset, int whence) {
	return 0;
}

uint32_t vga_write(vfs_node_t* node, uint32_t offset, uint32_t size, uint8_t* buf) {
	for (uint32_t i = 0; i < size; i++) {
		vga_putchar((char)buf[i]);
	}
	return size;
}