/////////////////////////////////////////////////////////////////////////
// $Id$
/////////////////////////////////////////////////////////////////////////
//
//  Copyright (C) 2018  The Bochs Project
//
//  This library is free software; you can redistribute it and/or
//  modify it under the terms of the GNU Lesser General Public
//  License as published by the Free Software Foundation; either
//  version 2 of the License, or (at your option) any later version.
//
//  This library is distributed in the hope that it will be useful,
//  but WITHOUT ANY WARRANTY; without even the implied warranty of
//  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
//  Lesser General Public License for more details.
//
//  You should have received a copy of the GNU Lesser General Public
//  License along with this library; if not, write to the Free Software
//  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301 USA

// DDC stub (when ready, this code should return the VESA EDID for the
// Bochs plug&play monitor)

// Define BX_PLUGGABLE in files that can be compiled into plugins.  For
// platforms that require a special tag on exported symbols, BX_PLUGGABLE
// is used to know when we are exporting symbols and when we are importing.
#define BX_PLUGGABLE

#include "bochs.h"
#include "ddc.h"

#define LOG_THIS

bx_ddc_c::bx_ddc_c(void)
{
  put("DDC");
  s.DCKhost = 1;
  s.DDAhost = 1;
  s.DCKmon = 1;
  s.DDAmon = 1;
  s.retval = 0x0f;
}

bx_ddc_c::~bx_ddc_c(void)
{
}

Bit8u bx_ddc_c::read()
{
  return s.retval;
}

void bx_ddc_c::write(bx_bool dck, bx_bool dda)
{
  if (dck != s.DCKhost) {
    BX_INFO(("DCK now %s", dck ? "inactive":"active low"));
    s.DCKhost = dck;
  }
  if (dda != s.DDAhost) {
    BX_INFO(("DDA now %s", dda ? "inactive":"active low"));
    s.DDAhost = dda;
  }
  combine_signals();
}

void bx_ddc_c::combine_signals()
{
  s.retval = (s.DCKhost & s.DCKmon) << 2;
  s.retval |= ((s.DDAhost & s.DDAmon) << 3);
  s.retval |= ((s.DDAhost << 1) | s.DCKhost);
}