[Teton] Draw a green square into the framebuffer.

sys/teton/framebuffer/framebuffer.cpp

@@ -0,0 +1,15 @@
+#include "framebuffer/framebuffer.h"
+
+#include <mammoth/memory_region.h>
+
+Framebuffer::Framebuffer(const FramebufferInfo& info) : fb_info_(info) {
+  uint64_t buff_size_bytes = fb_info_.height() * fb_info_.pitch();
+  MappedMemoryRegion region = MappedMemoryRegion::DirectPhysical(
+      fb_info_.address_phys(), buff_size_bytes);
+  fb_ = reinterpret_cast<uint32_t*>(region.vaddr());
+}
+
+void Framebuffer::DrawPixel(uint32_t row, uint32_t col, uint32_t pixel) {
+  // Div by 4 because pitch is in bytes and fb_ is a 32bit array.
+  fb_[(row * fb_info_.pitch() / 4) + col] = pixel;
+}