Linked-in drivers in Enea OSE

Writing Linked-in drivers that also work on Enea OSE is very similar for how you would do it for Unix. The difference from Unix is that driver_select, ready_input and ready_output all work with signals instead of file descriptors. This means that the driver_select is used to specify which type of signal should trigger calls to ready_input/ready_output. The functions described below are available to driver programmers on Enea OSE to facilitate this.


union SIGNAL
See the Enea OSE SPI documentation for a description.
See the Enea OSE SPI documentation for a description.
The ErlDrvEvent is a handle to a signal number and id combination. It is passed to driver_select(3).
This is the id used to associate a specific signal to a certain driver instance.


union SIGNAL * erl_drv_ose_get_signal(ErlDrvEvent drv_event)

Fetch the next signal associated with drv_event. Signals will be returned in the order which they were received and when no more signals are available NULL will be returned. Use this function in the ready_input/ready_output callbacks to get signals.

ErlDrvEvent erl_drv_ose_event_alloc(SIGSELECT signo, ErlDrvOseEventId id, ErlDrvOseEventId (*resolve_signal)(union SIGNAL* sig), void *extra)

Create a new ErlDrvEvent associated with signo, id and uses the resolve_signal function to extract the id from a signal with signo. The extra parameter can be used for additional data. See Signals in a Linked-in driver in the OSE User's Guide.

void erl_drv_ose_event_free(ErlDrvEvent drv_event)

Free a ErlDrvEvent. This should always be done in the stop_select callback when the event is no longer being used.

void erl_drv_ose_event_fetch(ErlDrvEvent drv_event, SIGSELECT *signo, ErlDrvOseEventId *id, void **extra)

Write the signal number, id and any extra data associated with drv_event into *signo and *id respectively. NULL can be also passed as signo or id in order to ignore that field.