C++ library for interacting with the Chrome OS Embedded Controller.
Each EC command is represented with a C++ class that conforms to the
EcCommandInterface interface. All EC commands are either synchronous or
"asynchronous". Asynchronous EC commands are commands that do not complete
immediately and require polling to get the result. Most EC commands are
synchronous.
Synchronous commands should inherit from the EcCommand class. Asynchronous
commands should inherit from the EcCommandAsync class.
Each EC command has a version number associated with it, which allows introducing new versions of commands while maintaining backward compatibility with older ECs that cannot be changed.
In order to abstract this complexity for consumers of libec, libec provides
a factory class called EcCommandFactory. EcCommandFactory can be used to
automatically instantiate the correct version of the command based on the
command version that the EC supports.
For example, EcCommandFactory::FpContextCommand uses
FpContextCommandFactory::Create to instantiate version 0 or version 1 of
the EC_CMD_FP_CONTEXT command, depending on what the EC supports.
All commands have a unit test with a name of <command>_test.cc. It's possible
to mock the response from the EC by mocking the EcCommand::Resp() method. For
a simple example, see the DisplayStateOfChargeCommandTest. For an example of
more advanced testing you can do with mocking, see the FpFrameCommandTest.
To add a new command, create files for your command called <command>.cc and
<command.h>, as well as a test file <command>_test.cc. Create a Command
class that inherits from EcCommand or EcCommandAsync. The template
arguments are the params and response structs for the command. For example,
the EC_CMD_DEVICE_EVENT command uses struct ec_params_device_event for
parameters and struct ec_response_device_event for the response, so the
DeviceEventCommand inherits from EcCommand<struct ec_params_device_event, struct response_device_event>.
Commands that don't have a request or response use EmptyParam as the
template parameter. See the DisplayStateOfChargeCommand for an example.
Commands that have variable length arrays in the params or response struct
need to redefine the struct so that it has a well-defined size. See
fp_template_params.h for an example. Please include a test to validate that
the two structs do not get out of sync. See fp_template_params_test.cc for
an example.