diff options
Diffstat (limited to 'README')
| -rw-r--r-- | README | 30 |
1 files changed, 30 insertions, 0 deletions
@@ -4213,6 +4213,36 @@ Please note that changes to some configuration parameters may take only effect after the next boot (yes, that's just like Windoze :-). +Callback functions for environment variables: +--------------------------------------------- + +For some environment variables, the behavior of u-boot needs to change +when their values are changed. This functionailty allows functions to +be associated with arbitrary variables. On creation, overwrite, or +deletion, the callback will provide the opportunity for some side +effect to happen or for the change to be rejected. + +The callbacks are named and associated with a function using the +U_BOOT_ENV_CALLBACK macro in your board or driver code. + +These callbacks are associated with variables in one of two ways. The +static list can be added to by defining CONFIG_ENV_CALLBACK_LIST_STATIC +in the board configuration to a string that defines a list of +associations. The list must be in the following format: + + entry = variable_name[:callback_name] + list = entry[,list] + +If the callback name is not specified, then the callback is deleted. +Spaces are also allowed anywhere in the list. + +Callbacks can also be associated by defining the ".callbacks" variable +with the same list format above. Any association in ".callbacks" will +override any association in the static list. You can define +CONFIG_ENV_CALLBACK_LIST_DEFAULT to a list (string) to define the +".callbacks" envirnoment variable in the default or embedded environment. + + Command Line Parsing: ===================== |