DAC_XGENIOCTRL
matroxfb_DAC_out(minfo, DAC_XGENIOCTRL, 0x00);
v = (matroxfb_DAC_in(minfo, DAC_XGENIOCTRL) & mask) | val;
matroxfb_DAC_out(minfo, DAC_XGENIOCTRL, v);