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void PPCVga::initialise()
{
  // Firstly get the screen device.
  // TODO: deal more cleanly with failure.
  OFDevice screen(OpenFirmware::instance().findDevice("screen"));

  // Get the 'chosen' device.
  OFDevice chosen(OpenFirmware::instance().findDevice("/chosen"));

  // Now we can get the MMU device from chosen.
  OFDevice mmu( chosen.getProperty("mmu") );

  // Get the (physical) framebuffer address.
  OFParam physFbAddr = screen.getProperty("address");

  // Create a mapping with OpenFirmware.
  /// \todo Something with VirtualAddressSpace here?
  mmu.executeMethod("map", 4,
                    reinterpret_cast<OFParam>(0x6a),
                    reinterpret_cast<OFParam>(0x01000000),
                    static_cast<OFParam>(m_pFramebuffer),
                    physFbAddr); // 0x6a = Uncached.

  // Find the device width, height and depth.
  m_Width = reinterpret_cast<uint32_t> ( screen.getProperty("width") );
  m_Height = reinterpret_cast<uint32_t> ( screen.getProperty("height") );
  m_Depth = reinterpret_cast<uint32_t> ( screen.getProperty("depth") );
  m_Stride = reinterpret_cast<uint32_t> ( screen.getProperty("linebytes") );

  if (m_Depth == 8)
  {
    for (int i = 0; i < 16; i++)
      m_pColours[i] = i;
  }
  else if (m_Depth == 16)
  {
    m_pColours[0] = RGB_16 (0x00, 0x00, 0x00); // Black
    m_pColours[1] = RGB_16 (0x00, 0x00, 0x99); // Blue
    m_pColours[2] = RGB_16 (0x00, 0x99, 0x00); // Green
    m_pColours[3] = RGB_16 (0x00, 0x99, 0x99); // Cyan
    m_pColours[4] = RGB_16 (0x99, 0x00, 0x00); // Red
    m_pColours[5] = RGB_16 (0x99, 0x00, 0x99); // Magenta
    m_pColours[6] = RGB_16 (0x99, 0x66, 0x00); // Brown
    m_pColours[7] = RGB_16 (0xBB, 0xBB, 0xBB); // Light grey
    m_pColours[8] = RGB_16 (0x99, 0x99, 0x99); // Dark grey
    m_pColours[9] = RGB_16 (0x00, 0x00, 0xFF); // Light blue
    m_pColours[10] =RGB_16 (0x00, 0xFF, 0x00); // Light green
    m_pColours[11] =RGB_16 (0x00, 0xFF, 0xFF); // Light cyan
    m_pColours[12] =RGB_16 (0xFF, 0x00, 0x00); // Light red
    m_pColours[13] =RGB_16 (0xFF, 0x00, 0xFF); // Light magenta
    m_pColours[14] =RGB_16 (0xFF, 0xFF, 0x00); // Light brown / yellow
    m_pColours[15] =RGB_16 (0xFF, 0xFF, 0xFF); // White
    m_Stride /= 2; // 16bpp = 2 bytes per pixel.
  }

  // Clear the text framebuffer.
  uint16_t clear = ' ';
  for (unsigned int i = 0; i < (m_Width/FONT_WIDTH)*(m_Height/FONT_HEIGHT); i++)
  {
    m_pTextBuffer[i] = clear;
  }

  // Clear the graphics framebuffer.
  uint16_t *p16Fb = reinterpret_cast<uint16_t*> (m_pFramebuffer);
  uint32_t *p32Fb = reinterpret_cast<uint32_t*> (m_pFramebuffer);
  for (unsigned int i = 0; i < m_Stride*m_Height; i++)
  {
    switch (m_Depth)
    {
      case 8:
        m_pFramebuffer[i] = 0x00;
        break;
      case 16:
        p16Fb[i] = 0x0000;
        break;
      case 32:
        p32Fb[i] = 0x00000000;
        break;
    }
  }

}