I/O Interrupt Scanning

[Andrew Johnson <anj@mail.ast.cam.ac.uk>]

Question: Is it legal to call scanIoInit from within a get_ioint_info device 
routine?

I am writing a driver which could conceivably have up to 255 different I/O 
interrupt event sources (although they all come through one ISR).

At present within the device initialisation routine I check if a record is set 
to I/O Interrupt scanning and call scanIoInit if it is.  For a record which 
started out as I/O Interrupt I can subsequently set the SCAN field to Passive, 
I/O Intr or one of the periodics.

However for records which are not set to I/O Interrupt scan at initialisation, I 
don't call scanIoInit, so if I later try to change the SCAN field on these 
records to I/O Interrupt, get_ioint_info has to return an error and the SCAN 
field will not be altered.

For performance reasons I don't want to set up the IOSCANPVT unless the database 
application needs it, so I wondered whether can I call scanIoInit from within 
the get_ioint_info device routine, then store and return the IOSCANPVT pointer 
immediately?

- Andrew

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