This is an old revision of the document!
At this current time the only way to allow channels 12,13,14 is to make your own custom firmware
Very simple - once you get all the stuff installed
Do a “make menuconfig”
Goto Kernel Modules → Wireless Drivers
Highlight kmod-ath and hit enter, Configuration and enter
Choose this setting:
[*] Force Atheros drivers to respect the user's regdomain settings
I don't see an option to enable this for Broadcom, but I only am compiling for my Atheros devices
The above is for OpenWRT images.
For building your own Gargoyle images, follow the Documentation section for Developers - clone the git, setup build environment, then do – make custom – and you can follow the above to goto Kernel Modules → Wireless Drivers, etc.
Even easier - you can edit the config.in files under the target directories and set this option: CONFIG_ATH_USER_REGD=y