This implements a simple hwconfig infrastructure: an interface for software knobs to control hardware. This a is very simple implementation, i.e. it is implemented via the `hwconfig' environment variable. Later we could write some "hwconfig " commands, ncurses interface for Award BIOS-like interface, and frame-buffer interface for AMI GUI[1] BIOS-like interface with mouse support[2]. Current implementation details/limitations: 1. Doesn't support options dependencies and mutual exclusion. We can implement this by integrating apt-get[3] into Das U-Boot. But I haven't bothered yet. 2. Since we don't implement a hwconfig command, i.e. we're working with the environment directly, there is no way to tell that toggling a particular option will need a reboot to take effect. So, for now it's advised to always reboot the target after modifying the hwconfig variable. 3. We support hwconfig options with arguments. For example, set hwconfig "dr_usb:mode=peripheral,phy_type=ulpi" This selects three hwconfig options: 1. dr_usb - enable Dual-Role USB controller; 2. dr_usb_mode:peripheral - USB in Function mode; 3. dr_usb_phy_type:ulpi - USB should work with ULPI PHYs. The purpose of this simple implementation is to refine the internal API and then we can continue improving the user experience by adding more mature interfaces, like a hwconfig command with bells and whistles. Or not adding, if we feel that the current interface fits people's needs. [1] http://en.wikipedia.org/wiki/American_Megatrends [2] Regarding ncurses and GUI with mouse support -- I'm just kidding. [3] The comment regarding apt-get is also a joke, meaning that dependency tracking could be non-trivial. For example, for enabling HW feature X we may need to disable Y, and turn Z into reduced mode (like RMII-only interface for ethernet, no MII). It's quite trivial to implement simple cases though.