Created attachment 333720 [details, diff] patch to enable tpacpi::micmute Please include the attached patch in genpatches. Ubuntu had it for a while and looks for inclusion (https://patchwork.kernel.org/patch/1036972/), but at the current state it is unclear if mic leds should actually be handled inside the alsa module. I had it in my user-patches for a while and it works great.
Released in gentoo-sources-3.7.6