Thanks to Benjamin's help and his neat patch which allows tempering with
quirks through sysfs, I got the device
eGalax 0eef:a001
to work. It works with the quirks
MT_QUIRK_SLOT_IS_CONTACTID | MT_QUIRK_ALWAYS_VALID ( = 18 )
so, using Benjamin's interface:
(1) Adding the device with
$ cd '/sys/modules/hid_multitouch/driver/hid:hid-multitouch'
$ echo "3 0eef a001 1" > new_id
(2) Setting the quirks with
$ echo 18 > '0003:0EEF:A001.0001/quirks'
That's it. The device works!
regards,
Cedric