Option API

The option API around the set_option(const char *name, void *val) and get_option(void *dest, const char *name) functions deprecated in favor of a type-safe API.

Historically, options were stored in RTC battery-backed CMOS RAM inside the chipset on PC platforms. Nowadays, options can also be stored in the same flash chip as the boot firmware or through some BMC interface.

The new type-safe option framework can be used by calling enum cb_err set_uint_option(const char *name, unsigned int value) and unsigned int get_uint_option(const char *name, const unsigned int fallback).

The default setting is OPTION_BACKEND_NONE, which disables any runtime configurable options. If supported by a mainboard, the USE_OPTION_TABLE and USE_MAINBOARD_SPECIFIC_OPTION_BACKEND choices are visible, and can be selected to enable runtime configurability.

Mainboard-specific option backend

Mainboards with a mainboard-specific (vendor-defined) method to access options can select HAVE_MAINBOARD_SPECIFIC_OPTION_BACKEND to provide implementations of the option API accessors. To allow choosing between multiple option backends, the mainboard-specific implementation should only be built when USE_MAINBOARD_SPECIFIC_OPTION_BACKEND is selected.

Where possible, using a generic, mainboard-independent mechanism should be preferred over reinventing the wheel in mainboard-specific code. The mainboard-specific approach should only be used when the option storage mechanism has to satisfy externally-imposed, vendor-defined constraints.