Comment 88 for bug 1428121

but your info did not have the channel mode to select 6ch , 8ch

http://git.kernel.org/cgit/linux/kernel/git/tiwai/sound.git/commit/sound/pci/hda?id=a07a949be6eb1c9aab06adaadce72dbd27b7d9cb

ALSA: hda - Fix multi-io channel mode management
The multi-io channels can vary not only from 1 to 6 but also may vary
from 6 to 8 or such.

spec->multi_ios = 1 when only blue Jack is used for retasking

 if (spec->multi_ios == 2) {
   for (i = 0; i < 2; i++)
    spec->private_dac_nids[spec->multiout.num_dacs++] =
     spec->multi_io[i].dac;
  } else if (spec->multi_ios) {
   spec->multi_ios = 0;
   badness += BAD_MULTI_IO;
  }