poll a device
void prefixpoll (int ps);
entry point routine is called every clock tick
in which the clock interrupted task-time processing.
It is used to get information from the device
without using interrupts.
integer that indicates the previous process's priority
when it was interrupted by the system clock
routine can seriously degrade system performance
because it causes an interrupt at every clock tick.
When possible, drivers should use an
entry point routine instead.
If the hardware doesn't generate interrupts,
you can use
to poll the device periodically
(such as once every ten clock ticks)
to lessen the impact on system performance.
Context and synchronization
The driver may not block
or access any process state information.
1, 2, 2mp, 3, 3mp, 4, 4mp, 5, 5mp, 6, 6mp
SVR5 DDI compatibility
entry point routine is not supported in DDI.
For STREAMS drivers,
this functionality is handled transparently
by the STREAMS head,
and TTY drivers
that call IOC_SELECT on SCO OpenServer
are implemented as STREAMS drivers in DDI.
DDI 7 and earlier non-STREAMS drivers
can implement similar functionality with the
entry point routine.
is not supported in DDI 8 and later versions.
If your driver needs to periodically
poll the hardware for certain conditions,
you can implement this with the
or with the synchronization variables
that are described in
``Synchronization variables'' in HDK Technical Reference.
Drivers that contain a
routine must have a p in the second column of the
19 June 2005
© 2005 The SCO Group, Inc. All rights reserved.
OpenServer 5 HDK - June 2005