Comment 31 for bug 1851518

Here's the full procedure to fix the headphones.

Step 1: Do the patch above, you can skip the [model] line if you wish since I found it had no effects on anything. Please note that the subsystem id can be different for various laptops (lenovo samsung etc...) so make sure you have the correct <vendor id> <subsystem id> <codec index> for the [codec] line values. To get these three values you can use https://github.com/jeremycline/hda-analyzer which requires python2 and pygtk module to run correctly. Another way is to use `sudo alsa-info.sh` command from terminal (press n when asked to upload information) to find the values. It will create a file under tmp folder which you can open via sudo vi or nano. Inside the file is a line !!HDA-Intel Codec information under which you will find the 3 values required for early patch to work, here's mine:
...
Address: 0
AFG Function Id: 0x1 (unsol 1)
Vendor Id: 0x10ec0298
Subsystem Id: 0x144dc169
...

PS: if you experience issues with typing in firefox/chromium then add the variable mentioned at the beginning of this post and restart.

PS2: if you are a hero, then see gannon's C patch doing this same thing in a more reliable way (custom kernel).