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transactions initiated by the CHARON core are processed by routines specified in the

chapi_out descriptor, and transactions initiated by the device instance are processed by

routines specified in the chapi_in descriptor. This is why a device instance must store the

data path to at least the chapi_in descriptor.

Both CHARON and the loadable component are allowed to omit (i.e. set to 0) some or all

entry points in the chapi_in and the chapi_out descriptors respectively. An entry point set

to zero is considered absent. An absent entry point for a certain operation means that the

operation is not supported and shall not be initiated by the counterpart.

2.6 Notes on threading

Any threading model maybe used in third party CHAPI device. The only restriction is to

follow the rules of calling CHAPI procedures – many of them require certain call conditions

(see 2.5, 3.4 for details). In general:

1) It is reasonable to perform any kind of I/O communication in one or a number of

separate backgroung threads depending on device specific;

2) It is reasonable to perform some kind of heavy calculations (packet processing for

network adapters, graphical processing for video adapters, etc) in a separate

dedicated background thread.