Implement VGA text-mode driver with memory statistics display (AI)
- Created VGA driver that writes to the 0xB8000 text-mode framebuffer.
Supports 80x25 display with 16 foreground/background colors, scrolling,
hardware cursor updates, and special characters (\n, \r, \t, \b).
- Provides vga_puts, vga_putchar, vga_put_hex, vga_put_dec, vga_set_color.
- Displays boot banner ("ClaudeOS v0.1 booting...") on screen clear.
- vga_show_mem_stats() prints total RAM, kernel start/end addresses, and
kernel size on the VGA display during boot.
- Registered as the first driver using REGISTER_DRIVER, proving the
driver framework works end-to-end (probe -> init lifecycle).
Tested: driver loads successfully, debug port confirms vga probe/init.
This commit is contained in:
AI
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src/vga.c
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230
src/vga.c
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/**
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* @file vga.c
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* @brief VGA text-mode driver implementation.
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*
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* Drives the standard VGA text-mode framebuffer at 0xB8000. The buffer
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* is an array of 80×25 16-bit values, where the low byte is the ASCII
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* character and the high byte encodes foreground and background color.
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*
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* This driver registers itself via the REGISTER_DRIVER macro and is
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* automatically discovered during boot.
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*/
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#include "vga.h"
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#include "driver.h"
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#include "port_io.h"
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#include "pmm.h"
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/** Base address of the VGA text-mode framebuffer. */
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#define VGA_BUFFER 0xB8000
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/** Pointer to the VGA framebuffer, treated as an array of uint16_t. */
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static uint16_t *vga_buffer = (uint16_t *)VGA_BUFFER;
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/** Current cursor row (0-based). */
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static uint8_t cursor_row = 0;
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/** Current cursor column (0-based). */
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static uint8_t cursor_col = 0;
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/** Current text attribute byte (foreground | background << 4). */
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static uint8_t text_attr = 0;
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/**
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* Create a VGA entry (character + attribute) for the framebuffer.
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*
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* @param c ASCII character.
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* @param attr Color attribute byte.
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* @return 16-bit VGA entry.
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*/
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static inline uint16_t vga_entry(char c, uint8_t attr) {
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return (uint16_t)c | ((uint16_t)attr << 8);
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}
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/**
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* Create a color attribute byte from foreground and background colors.
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*
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* @param fg Foreground color (0–15).
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* @param bg Background color (0–15).
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* @return Attribute byte.
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*/
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static inline uint8_t vga_color(vga_color_t fg, vga_color_t bg) {
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return (uint8_t)fg | ((uint8_t)bg << 4);
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}
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/**
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* Update the hardware cursor position via VGA I/O ports.
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*/
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static void update_cursor(void) {
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uint16_t pos = cursor_row * VGA_WIDTH + cursor_col;
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outb(0x3D4, 0x0F);
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outb(0x3D5, (uint8_t)(pos & 0xFF));
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outb(0x3D4, 0x0E);
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outb(0x3D5, (uint8_t)((pos >> 8) & 0xFF));
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}
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/**
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* Scroll the screen up by one line.
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*
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* The top line is discarded, all other lines move up, and the bottom
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* line is filled with spaces.
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*/
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static void scroll(void) {
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/* Move all lines up by one */
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for (int i = 0; i < (VGA_HEIGHT - 1) * VGA_WIDTH; i++) {
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vga_buffer[i] = vga_buffer[i + VGA_WIDTH];
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}
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/* Clear the last line */
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uint16_t blank = vga_entry(' ', text_attr);
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for (int i = (VGA_HEIGHT - 1) * VGA_WIDTH; i < VGA_HEIGHT * VGA_WIDTH; i++) {
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vga_buffer[i] = blank;
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}
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cursor_row = VGA_HEIGHT - 1;
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}
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void vga_clear(void) {
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uint16_t blank = vga_entry(' ', text_attr);
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for (int i = 0; i < VGA_WIDTH * VGA_HEIGHT; i++) {
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vga_buffer[i] = blank;
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}
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cursor_row = 0;
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cursor_col = 0;
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update_cursor();
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}
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void vga_set_color(vga_color_t fg, vga_color_t bg) {
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text_attr = vga_color(fg, bg);
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}
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void vga_putchar(char c) {
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if (c == '\n') {
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cursor_col = 0;
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cursor_row++;
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} else if (c == '\r') {
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cursor_col = 0;
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} else if (c == '\t') {
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cursor_col = (cursor_col + 8) & ~7;
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if (cursor_col >= VGA_WIDTH) {
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cursor_col = 0;
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cursor_row++;
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}
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} else if (c == '\b') {
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if (cursor_col > 0) {
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cursor_col--;
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vga_buffer[cursor_row * VGA_WIDTH + cursor_col] = vga_entry(' ', text_attr);
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}
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} else {
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vga_buffer[cursor_row * VGA_WIDTH + cursor_col] = vga_entry(c, text_attr);
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cursor_col++;
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if (cursor_col >= VGA_WIDTH) {
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cursor_col = 0;
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cursor_row++;
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}
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}
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if (cursor_row >= VGA_HEIGHT) {
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scroll();
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}
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update_cursor();
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}
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void vga_puts(const char *str) {
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while (*str) {
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vga_putchar(*str);
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str++;
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}
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}
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void vga_put_hex(uint32_t val) {
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const char *hex = "0123456789ABCDEF";
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vga_putchar('0');
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vga_putchar('x');
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for (int i = 28; i >= 0; i -= 4) {
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vga_putchar(hex[(val >> i) & 0xF]);
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}
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}
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void vga_put_dec(uint32_t val) {
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if (val == 0) {
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vga_putchar('0');
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return;
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}
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char buf[12];
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int pos = 0;
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while (val > 0) {
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buf[pos++] = '0' + (val % 10);
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val /= 10;
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}
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/* Print in reverse */
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while (pos > 0) {
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vga_putchar(buf[--pos]);
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}
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}
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void vga_show_mem_stats(void) {
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uint32_t mem_kb = pmm_get_memory_size() + 1024; /* total including lower */
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vga_set_color(VGA_LIGHT_CYAN, VGA_BLACK);
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vga_puts("=== ClaudeOS Memory Statistics ===\n");
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vga_set_color(VGA_WHITE, VGA_BLACK);
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vga_puts(" Total RAM: ");
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vga_put_dec(mem_kb);
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vga_puts(" KiB (");
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vga_put_dec(mem_kb / 1024);
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vga_puts(" MiB)\n");
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vga_puts(" Kernel start: ");
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extern uint32_t _kernel_start;
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vga_put_hex((uint32_t)&_kernel_start);
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vga_puts("\n");
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vga_puts(" Kernel end: ");
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extern uint32_t _kernel_end;
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vga_put_hex((uint32_t)&_kernel_end);
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vga_puts("\n");
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uint32_t kernel_size = (uint32_t)&_kernel_end - (uint32_t)&_kernel_start;
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vga_puts(" Kernel size: ");
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vga_put_dec(kernel_size / 1024);
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vga_puts(" KiB\n");
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vga_set_color(VGA_LIGHT_CYAN, VGA_BLACK);
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vga_puts("==================================\n");
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vga_set_color(VGA_LIGHT_GREY, VGA_BLACK);
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}
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/* --- Driver registration --- */
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/**
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* VGA probe: always succeeds since VGA text mode is always available
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* on the target platform (i386).
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*/
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static driver_probe_result_t vga_probe(void) {
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return DRIVER_PROBE_OK;
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}
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int vga_init(void) {
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text_attr = vga_color(VGA_LIGHT_GREY, VGA_BLACK);
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vga_clear();
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vga_set_color(VGA_LIGHT_GREEN, VGA_BLACK);
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vga_puts("ClaudeOS v0.1 booting...\n\n");
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vga_set_color(VGA_LIGHT_GREY, VGA_BLACK);
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return 0;
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}
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/** VGA driver descriptor. */
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static const driver_t vga_driver = {
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.name = "vga",
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.probe = vga_probe,
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.init = vga_init,
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};
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REGISTER_DRIVER(vga_driver);
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