From 38f87f12c59b16467181c410e180087b5ec0d828 Mon Sep 17 00:00:00 2001
From: Aaron Lindsay <aaron@aclindsay.com>
Date: Fri, 7 Sep 2012 23:54:04 -0400
Subject: [PATCH] Add basic framebuffer support (probably not working right
 yet?)

Possibly (probably) calculating wrong pixel values, addresses.
---
 include/framebuffer.h | 27 +++++++++++++++++++++++++++
 kernel/framebuffer.c  | 31 +++++++++++++++++++++++++++++++
 2 files changed, 58 insertions(+)
 create mode 100644 include/framebuffer.h
 create mode 100644 kernel/framebuffer.c

diff --git a/include/framebuffer.h b/include/framebuffer.h
new file mode 100644
index 0000000..ba91b03
--- /dev/null
+++ b/include/framebuffer.h
@@ -0,0 +1,27 @@
+#ifndef FRAMEBUFFER_H
+#define FRAMEBUFFER_H
+
+// 1, 2, and 4 bit color are currently unsupported
+//#define FB_COLOR_DEPTH_1  1
+//#define FB_COLOR_DEPTH_2  2
+//#define FB_COLOR_DEPTH_4  4
+#define FB_COLOR_DEPTH_8  8
+#define FB_COLOR_DEPTH_16 16
+#define FB_COLOR_DEPTH_24 24
+
+struct fbdev {
+	unsigned int pixelwidth, pixelheight;
+	unsigned int color_depth;
+	void *fbaddr; //start address of the frame buffer in memory
+	void *device_ptr; //passed into device
+};
+
+struct fb {
+	unsigned int width, height;
+	unsigned int color_depth;
+	struct fbdev *device;
+};
+
+int fb_write_pixel(struct fb *f, unsigned int x, unsigned int y, unsigned int r, unsigned int g, unsigned int b);
+
+#endif /* FRAMEBUFFER_H */
diff --git a/kernel/framebuffer.c b/kernel/framebuffer.c
new file mode 100644
index 0000000..ef6f175
--- /dev/null
+++ b/kernel/framebuffer.c
@@ -0,0 +1,31 @@
+#include <framebuffer.h>
+
+int fb_write_pixel_8bit(struct fb *f, unsigned int x, unsigned int y, unsigned int r, unsigned int g, unsigned int b) {
+	unsigned char pixel = (((r >> 6) << 4) & 0x30) | (((b >> 6) << 2) & 0xC) | ((g >> 6) & 0x3);
+	((char*) (f->device->fbaddr))[y*f->device->pixelwidth + x] = pixel;
+	return 0;
+}
+
+int fb_write_pixel_16bit(struct fb *f, unsigned int x, unsigned int y, unsigned int r, unsigned int g, unsigned int b) {
+	unsigned int pixel = (((r >> 3) << 10) & 0x7BF6) | (((b >> 3) << 5) & 0x3E0) | ((g >> 3) & 0x1F);
+	((char*)f->device->fbaddr)[(y*f->device->pixelwidth + x) << 1] = (char)pixel;
+	((char*)f->device->fbaddr)[((y*f->device->pixelwidth + x) << 1) + 1] = (char)(pixel >> 8);
+	return 0;
+}
+
+int fb_write_pixel_24bit(struct fb *f, unsigned int x, unsigned int y, unsigned int r, unsigned int g, unsigned int b) {
+	((char*)f->device->fbaddr)[(y*f->device->pixelwidth + x)*3] = (char)r;
+	((char*)f->device->fbaddr)[(y*f->device->pixelwidth + x)*3 + 1] = (char)b;
+	((char*)f->device->fbaddr)[(y*f->device->pixelwidth + x)*3 + 2] = (char)g;
+	return 0;
+}
+
+int fb_write_pixel(struct fb *f, unsigned int x, unsigned int y, unsigned int r, unsigned int g, unsigned int b) {
+	if (f->device->color_depth == FB_COLOR_DEPTH_8)
+		return fb_write_pixel_8bit(f, x, y, r, g, b);
+	else if (f->device->color_depth == FB_COLOR_DEPTH_16)
+		return fb_write_pixel_16bit(f, x, y, r, g, b);
+	else if (f->device->color_depth == FB_COLOR_DEPTH_24)
+		return fb_write_pixel_24bit(f, x, y, r, g, b);
+	return -1;
+}