From 4a7562c22a7365342754beed8fdebab0350bd256 Mon Sep 17 00:00:00 2001
From: Danny Holman <dholman@gymli.org>
Date: Fri, 16 Feb 2024 12:37:45 -0600
Subject: arch: i386: put framebuffer ops in own file

Move all operations related to the x86 framebuffer into its own set of
files. This makes the TTY layer more architecture agnostic.

Signed-off-by: Danny Holman <dholman@gymli.org>
---
 arch/i386/kernel/framebuffer.c | 105 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 105 insertions(+)
 create mode 100644 arch/i386/kernel/framebuffer.c

(limited to 'arch/i386/kernel/framebuffer.c')

diff --git a/arch/i386/kernel/framebuffer.c b/arch/i386/kernel/framebuffer.c
new file mode 100644
index 0000000..602bddb
--- /dev/null
+++ b/arch/i386/kernel/framebuffer.c
@@ -0,0 +1,105 @@
+#include <kernel/vga.h>
+#include <kernel/paging.h>
+#include <kernel/pic.h>
+#include <kernel/string.h>
+#include <stddef.h>
+#include <stdint.h>
+
+static const size_t VGA_WIDTH = 80;
+static const size_t VGA_HEIGHT = 25;
+static uint16_t *const VGA_MEMORY = (uint16_t*)0xC03FF000;
+
+static size_t fb_row;
+static size_t fb_column;
+static uint8_t fb_color;
+static uint16_t *framebuffer;
+
+void _enable_cursor(uint8_t cursor_start, uint8_t cursor_end) {
+        outb(0x3D4, 0x0A);
+        outb(0x3D5, (inb(0x3D5) & 0xC0) | cursor_start);
+
+        outb(0x3D4, 0x0B);
+        outb(0x3D5, (inb(0x3D5) & 0xE0) | cursor_end);
+}
+
+void _update_cursor(size_t x, size_t y) {
+        uint16_t pos = y * VGA_WIDTH + x;
+        
+        outb(0x3D4, 0x0F);
+        outb(0x3D5, (uint8_t)(pos & 0xFF));
+        outb(0x3D4, 0x0E);
+        outb(0x3D5, (uint8_t)((pos >> 8) & 0xFF));
+}
+
+void _fb_putentryat(unsigned char c, uint8_t color, size_t x, size_t y) {
+        const size_t index = y * VGA_WIDTH + x;
+        framebuffer[index] = vga_entry(c, color);
+}
+
+void _fb_scroll(void) {
+        for (size_t i = 0; i < VGA_HEIGHT-1; i++) {
+                for (size_t j = 0; j < VGA_WIDTH; j++)
+                        framebuffer[i * VGA_WIDTH + j] = VGA_MEMORY[(i+1) * VGA_WIDTH + j];
+        }
+}
+
+void fb_init(void) {
+        map_page(NULL, 0xB8000, (uintptr_t)VGA_MEMORY, 0x003);
+
+        fb_row = 0;
+        fb_column = 0;
+        fb_color = vga_entry_color(VGA_COLOR_LIGHT_GREY, VGA_COLOR_BLACK);
+        framebuffer = VGA_MEMORY;
+        for (size_t y = 0; y < VGA_HEIGHT; y++) {
+                for (size_t x = 0; x < VGA_WIDTH; x++)
+                        _fb_putentryat(' ', fb_color, x, y);
+        }
+        _enable_cursor(0, 0);
+        _update_cursor(0, 0);
+}
+
+void fb_setcolor(uint8_t color) {
+        fb_color = color;
+}
+
+void fb_setpos(int x, int y) {
+        fb_row = y;
+        fb_column = x;
+}
+
+void fb_putchar(char c) {
+        unsigned char uc = c;
+        switch (uc) {
+                case '\r':
+                        fb_column = 0;
+                        break;
+                case '\n':
+                        fb_column = 0;
+                        if (++fb_row == VGA_HEIGHT) {
+                                fb_row--;
+                                _fb_scroll();
+                        }
+                        break;
+                case '\t':
+                        fb_column += 4;
+                        if (++fb_column == VGA_WIDTH) {
+                                fb_column = 4;
+                                if (++fb_row == VGA_HEIGHT) {
+                                        fb_row--;
+                                        _fb_scroll();
+                                }
+                        }
+                        break;
+                default:
+                        _fb_putentryat(uc, fb_color, fb_column, fb_row);
+                        if (++fb_column == VGA_WIDTH) {
+                                fb_column = 0;
+                                if (++fb_row == VGA_HEIGHT) {
+                                        fb_row--;
+                                        _fb_scroll();
+                                }
+                        }
+                        break;
+        }
+        _update_cursor(fb_column, fb_row+1);
+}
-- 
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