It was completely unexpected. On a build with broken camera, I saw a lot of audioflinger-related spam in logcat during debugging. Even after fixing the camera, the spam was still there.

I ended up implementing audioflingerglue (lines 107-157 of http://piratepad.net/hadk-faq), which resulted in reducing the audioflinger logcat spam and increasing volumes.

Edit: If you're asking for FP2, another solution for increasing per-output/input gain is manually editing mixer_paths.xml in the device repo, rebuild hybris-hal, build_packages.sh, then install the updated packages to test. As I said, the audioflingerglue solution wasn't meant to be a solution for volume.

Edit2: While I'm at it, there's also kernel solution for managing output gain using sysfs interfaces. You can cherry-pick a commit like https://github.com/RealJohnGalt/andr...55cfa68e538fd7 or faux123's solution since fp2 also looks to use wcd9320. Then edit on the fly, test, and set using a systemd service or similar.