1 files changed, 108 insertions, 0 deletions
diff --git a/bootloader/vga.c b/bootloader/vga.c
new file mode 100644
index 0000000..355c17f
--- /dev/null
+++ b/bootloader/vga.c
@@ -0,0 +1,108 @@
+#include <efi.h>
+#include <efilib.h>
+
+#include "vga.h"
+
+void * EFIAPI SetVideoMode(int width, int height, int bitdepth)
+{
+  // find the location of the Graphics Output protocol to aquire a linear framebuffer
+  EFI_GUID EfiGOPGuid = EFI_GRAPHICS_OUTPUT_PROTOCOL_GUID;
+
+  struct _EFI_GRAPHICS_OUTPUT_PROTOCOL * Graphics = NULL;
+
+  Print(L"Searching for GOP\n");
+
+  EFI_STATUS localteprotocolstat = uefi_call_wrapper(BS->LocateProtocol, 3, &EfiGOPGuid, NULL, &Graphics);
+
+  if(localteprotocolstat != EFI_SUCCESS)
+  {
+    Print(L"Failed to locate GOP\n");
+  }
+
+  // we now search for a 1024x768 mode with a bit depth of 32bits
+  EFI_GRAPHICS_OUTPUT_PROTOCOL_MODE * GOPMode;
+
+  EFI_GRAPHICS_OUTPUT_MODE_INFORMATION * GOPInfo = NULL;
+
+  GOPMode = Graphics->Mode;
+
+  UINT32 MaxModes = GOPMode->MaxMode;
+
+  UINTN infosize = 0;
+
+  uefi_call_wrapper(Graphics->QueryMode, 4, Graphics, 0, &infosize, &GOPMode);
+
+  Print(L"Size of GOP Info: %d\n", infosize);
+
+  // print information about the available modes
+  UINT32 i;
+  uint64_t foundmode = 0;
+
+  for(i = 0; i < MaxModes; ++i)
+  {
+    uefi_call_wrapper(Graphics->QueryMode, 4, Graphics, i, &infosize, &GOPInfo);
+
+    /*
+    switch(GOPInfo->PixelFormat)
+    {
+      case PixelRedGreenBlueReserved8BitPerColor:
+        Print(L"RGBZ\n");
+        break;
+      case PixelBlueGreenRedReserved8BitPerColor:
+        Print(L"BGRZ\n");
+        break;
+      case PixelBitMask:
+        Print(L"By Mask\n");
+        break;
+      case PixelBltOnly:
+        Print(L"Only Blt\n"); // this mode doesn't expose a linear framebuffer
+      default:
+        Print(L"Unknown\n");
+        break;
+    }
+    */
+    if(GOPInfo->HorizontalResolution == width && GOPInfo->VerticalResolution == height)
+    {
+      foundmode = i;
+    }
+
+    // Print(L"Mode %d:   Width: %d Height: %d\n", i, GOPInfo->HorizontalResolution, GOPInfo->VerticalResolution);
+  }
+
+  uefi_call_wrapper(Graphics->SetMode, 2, Graphics, foundmode); // hardcoded to mode 2(1024x768), this is only tue for the cirrus vga that qemu exposes
+  uefi_call_wrapper(ST->ConOut->ClearScreen, 1, ST->ConOut); // clear the screen
+  //uefi_call_wrapper(Graphics->QueryMode, 4, Graphics, i, &infosize, &GOPInfo);
+  Print(L"Width: %d Height: %d Format: ", Graphics->Mode->Info->HorizontalResolution, Graphics->Mode->Info->VerticalResolution);
+  switch(Graphics->Mode->Info->PixelFormat)
+  {
+    case PixelRedGreenBlueReserved8BitPerColor:
+      Print(L"RGBZ\n");
+      break;
+    case PixelBlueGreenRedReserved8BitPerColor:
+      Print(L"BGRZ\n");
+      break;
+    case PixelBitMask:
+      Print(L"By Mask\n");
+      break;
+    case PixelBltOnly:
+      Print(L"Only Blt\n");
+    default:
+      Print(L"Unknown\n");
+      break;
+  }
+
+  Print(L"RedBitmask: %d\n", Graphics->Mode->Info->PixelInformation.RedMask);
+  Print(L"GreenBitmask: %d\n", Graphics->Mode->Info->PixelInformation.GreenMask);
+  Print(L"BlueBitmask: %d\n", Graphics->Mode->Info->PixelInformation.BlueMask);
+  Print(L"ReservedBitmask: %d\n", Graphics->Mode->Info->PixelInformation.ReservedMask);
+  Print(L"Pixels Per ScanLine: %d\n", Graphics->Mode->Info->PixelsPerScanLine);
+
+  // pixels seem to be 4 bytes wide(32bits)
+  // format seems to be RGB Reserved
+
+  //Print(L"FrameBuffer Size: %d\n", Graphics->Mode->FrameBufferSize);
+  //Print(L"FrameBuffer Addr: %d\n", Graphics->Mode->FrameBufferBase);
+
+  return (void*)Graphics->Mode->FrameBufferBase;
+}
+