Lenovo X270 with HDA ALC298

[Yasushi SHOJI]

Hi all,

I noticed that my 3 years old Lenovo X270 with Intel HDA & RealTek
ALC298 doesn't work with 3.5 mm audio combo jack with 4 pole CTIA. A
bit of googling showed me that `snd-hda-intel` module can take some
options like `model` to run some fix ups. and I have found that
`model=alc298-dell1` seems to at least work. But its gain is way too
low.  It's mostly just noise.  It sounds like my mic is on the
line-in.

So, I opened `patch_realtek.c` to see what's going on. I found the
following but not sure what the values for `.v.pins` are for.

```
[ALC298_FIXUP_DELL1_MIC_NO_PRESENCE] = {
.type = HDA_FIXUP_PINS,
.v.pins = (const struct hda_pintbl[]) {
{ 0x18, 0x01a1913c }, /* use as headset mic, without its own jack detect */
{ 0x1a, 0x01a1913d }, /* use as headphone mic, without its own jack detect */
{ }
},
.chained = true,
.chain_id = ALC269_FIXUP_HEADSET_MODE
},
```

In `apply_fix(), these `.v.pins` values are passed to
`snd_hda_apply_pincfgs()` but I can't find what values mean.  Would
someone please enlighten me?

My questions are

1) How can I found out which pin goes where.  There is x270 schematics
   on the net but not sure it's correct.

2) What does the value, ie, 0x01a1913d, represent?

Thanks,
-- 
              yashi