Dears,
thanks to some indications from the user 'Raymond' in the alsa bug
reporting system (an alsa developer?) I've found that a fully working
model for the module snd-hda-intel is 'toshiba-s06'. Now also the
internal microphone works well (gnome-sound-recorder, skype,...).
https://bugtrack.alsa-project.org/alsa-bug/view.php?id=4131#bugnotes
Create a file (by root or using 'sudo') in /etc/modprobe.d/ with a line
like 'options snd-hda-intel model=toshiba-s06' then reboot (or unload
and reload the module). Check in alsamixer that the capture source is
'Int DMic'. Enjoy! :)ice