[Teton] Draw a green square into the framebuffer.

sys/teton/CMakeLists.txt

@@ -1,4 +1,5 @@
 add_executable(teton
+  framebuffer/framebuffer.cpp
   teton.cpp
   )
 

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;
+}

sys/teton/framebuffer/framebuffer.h

@@ -0,0 +1,16 @@
+#pragma once
+
+#include <yellowstone/yellowstone.yunq.h>
+
+class Framebuffer {
+ public:
+  Framebuffer(const FramebufferInfo& info);
+
+  void DrawPixel(uint32_t row, uint32_t col, uint32_t pixel);
+
+ private:
+  // FIXME: Implement Yunq copy or move so we
+  // don't have to store a reference here.
+  const FramebufferInfo& fb_info_;
+  uint32_t* fb_;
+};

sys/teton/teton.cpp

@@ -2,6 +2,8 @@
 #include <mammoth/init.h>
 #include <yellowstone/yellowstone.yunq.client.h>
 
+#include "framebuffer/framebuffer.h"
+
 uint64_t main(uint64_t init_port) {
   ParseInitPort(init_port);
 
@@ -12,8 +14,17 @@ uint64_t main(uint64_t init_port) {
 
   FramebufferInfo framebuffer;
   RET_ERR(client.GetFramebufferInfo({}, framebuffer));
-  dbgln("FB addr {x}, width {} , height {}", framebuffer.address_phys(),
-        framebuffer.width(), framebuffer.height());
+  dbgln("FB addr {x}, bpp {}, width {} , height {}, pitch {}",
+        framebuffer.address_phys(), framebuffer.bpp(), framebuffer.width(),
+        framebuffer.height(), framebuffer.pitch());
+
+  Framebuffer fbuf(framebuffer);
+
+  for (uint64_t r = 0; r < 20; r++) {
+    for (uint64_t c = 0; c < 20; c++) {
+      fbuf.DrawPixel(r, c, 0x0000FF00);
+    }
+  }
 
   // 2. Parse a font file.