Comment 55 for bug 1302090

https://git.kernel.org/cgit/linux/kernel/git/tiwai/sound.git/commit/sound/pci/hda?id=73bdd597823e2231dc882577dbbaf8df92fe1775

for dell laptop with combo jack which use 0x1b for headset mic

which is similar to your configuration without headhone jack and mic jack

+ [ALC668_FIXUP_DELL_MIC_NO_PRESENCE] = {
+ .type = HDA_FIXUP_PINS,
+ .v.pins = (const struct hda_pintbl[]) {
+ { 0x19, 0x03a1913d }, /* use as headphone mic, without its own jack detect */
+ { 0x1b, 0x03a1113c }, /* use as headset mic, without its own jack detect */
+ { }
+ },
+ .chained = true,
+ .chain_id = ALC668_FIXUP_HEADSET_MODE
+ },