cowos attempted gdt, but at least we have vga drivers now

kernel/drivers/video/vga.c

@@ -1,61 +1,118 @@
 #include <drivers/video/vga.h>
-/* #include <bootloader.h> */
-#include <string.h>
 
-/* for frame buffer
-static volatile struct limine_framebuffer_request limineFBreq = {
-    .id = LIMINE_FRAMEBUFFER_REQUEST, .revision = 0};
-*/
-
-size_t term_row;
-size_t term_col;
-uint8_t term_color;
-uint16_t* term_buf = (uint16_t*)VGA_MEMORY;
-
-void
-term_init(void)
+// Helper functions for port IO
+static inline void
+outb(uint16_t port, uint8_t val)
 {
-        term_row = 0;
-        term_col = 0;
-        term_color = vga_entry_color(VGA_COLOR_WHITE, VGA_COLOR_BLACK);
+   	__asm__ volatile ("outb %0, %1" : : "a"(val), "Nd"(port));
+}
 
-        for (size_t y = 0; y < VGA_HEIGHT; y++) {
-                for (size_t x = 0; x < VGA_WIDTH; x++) {
-                        const size_t index = y * VGA_WIDTH + x;
-                        term_buf[index] = vga_entry(' ', term_color);
-                }
-        }
+static inline uint8_t
+inb(uint16_t port)
+{
+    	uint8_t ret;
+    	__asm__ volatile ("inb %1, %0" : "=a"(ret) : "Nd"(port));
+    	return ret;
+}
+
+// Write vga registers for mode change
+static void
+write_regs(uint8_t *regs)
+{
+    	unsigned i;
+    	
+    	// Write misc output register
+    	outb(VGA_MISC_WRITE, *regs);
+    	regs++;
+    	
+    	// Write sequencer registers (5 registers)
+    	for (i = 0; i < 5; i++) {
+    	    outb(VGA_SEQ_INDEX, i);
+    	    outb(VGA_SEQ_DATA, *regs);
+    	    regs++;
+    	}
+    	
+    	// Unlock CRTC registers 0-7 by clearing protect bit
+    	outb(VGA_CRTC_INDEX, 0x03);
+    	outb(VGA_CRTC_DATA, inb(VGA_CRTC_DATA) | 0x80);
+    	outb(VGA_CRTC_INDEX, 0x11);
+    	outb(VGA_CRTC_DATA, inb(VGA_CRTC_DATA) & ~0x80);
+    	
+    	// Update the register values to match
+    	regs[0x03] = regs[0x03] | 0x80;
+    	regs[0x11] = regs[0x11] & ~0x80;
+    	
+    	// Write CRTC registers (25 registers)
+    	for (i = 0; i < 25; i++) {
+    	    outb(VGA_CRTC_INDEX, i);
+    	    outb(VGA_CRTC_DATA, *regs);
+    	    regs++;
+    	}
+    	
+    	// Write graphics controller registers (9 registers)
+    	for (i = 0; i < 9; i++) {
+    	    outb(VGA_GC_INDEX, i);
+    	    outb(VGA_GC_DATA, *regs);
+    	    regs++;
+    	}
+    	
+    	// Write attribute controller registers (21 registers)
+    	for (i = 0; i < 21; i++) {
+    	    inb(VGA_INSTAT_READ);  // Reset flip-flop
+    	    outb(VGA_AC_INDEX, i);
+    	    outb(VGA_AC_WRITE, *regs);
+    	    regs++;
+    	}
+    	
+    	// Enable video display
+    	inb(VGA_INSTAT_READ);
+    	outb(VGA_AC_INDEX, 0x20);
 }
 
 void
-term_setcolor(uint8_t color)
+vga_set_mode_13h(void)
 {
-        term_color = color;
+    	// Register values for VGA mode 13h (320x200, 256 colors)
+    	// Order: Misc, Seq[5], CRTC[25], GC[9], AC[21] 
+    	static uint8_t mode_320x200x256[] = {
+    	    // Misc output register
+    	    0x63,
+    	    // Sequencer registers
+    	    0x03, 0x01, 0x0F, 0x00, 0x0E,
+    	    // CRTC registers
+    	    0x5F, 0x4F, 0x50, 0x82, 0x54, 0x80, 0xBF, 0x1F,
+    	    0x00, 0x41, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+    	    0x9C, 0x0E, 0x8F, 0x28, 0x40, 0x96, 0xB9, 0xA3,
+    	    0xFF,
+    	    // Graphics controller registers 
+    	    0x00, 0x00, 0x00, 0x00, 0x00, 0x40, 0x05, 0x0F,
+    	    0xFF,
+    	    // Attribute controller registers 
+    	    0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
+    	    0x08, 0x09, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F,
+    	    0x41, 0x00, 0x0F, 0x00, 0x00
+    	};
+    	
+    	write_regs(mode_320x200x256);
 }
 
 void
-term_putentryat(char c, uint8_t color, size_t x, size_t y)
+vga_put_pixel(uint16_t x, uint16_t y, uint8_t color)
 {
-         const size_t index = y * VGA_HEIGHT + x;
-         term_buf[index] = vga_entry(c, color);
+    	// check bounds 
+    	if (x >= VGA_WIDTH || y >= VGA_HEIGHT) return;
+    	
+    	// Direct write to video memory: offset = y * 320 + x
+    	uint8_t *vga = (uint8_t *)VGA_GRAPHICS_BUFFER;
+    	vga[y * VGA_WIDTH + x] = color;
 }
 
 void
-term_putchar(char c)
+vga_clear_screen(uint8_t color)
 {
-        term_putentryat(c, term_color, term_col, term_row);
-        if (++term_col == VGA_WIDTH) {
-                term_col = 0;
-                if (++term_row == VGA_HEIGHT) {
-                        term_row = 0;
-                }
-        }
-}
-
-void
-term_writestr(const char* data)
-{
-        for (size_t i = 0; data[i] != '\0'; i++) {
-                term_putchar(data[i]);
-        }
+    	uint8_t *vga = (uint8_t *)VGA_GRAPHICS_BUFFER;
+    	// fill entire buffer (64k pixels)
+    	for (int i = 0; i < VGA_WIDTH * VGA_HEIGHT; i++) {
+    	    vga[i] = color;
+    	}
 }