Mac OS 8.5 Technote: Part XIX Copyright 1998 by Apple Computer, Inc. All Rights Reserved. [Previous section] [Mac OS 8.5 Contents Page] [Next section]

Inside the System File (Continued) Driver Services Library DriverServicesLib provides utility routines for native drivers ('ndrv's). The following improvements in virtual memory support have been added to the DriverServicesLib: PrepareMemoryForIO now uses LockMemoryForOutput instead of LockMemory when the IOPreparationOptions are kIOIsOutput, but not kIOIsInput. With Mac OS 8.5, GetPageInformation returns the kPageIsLockedResident (kPageIsLocked) PageStateInformation bit correctly. When Virtual Memory is on, kPageIsLockedResident indicates that a page has been locked with LockMemory, or LockMemoryForOutput. Before Mac OS 8.5, resident pages with the kPageIsInMemory (kPageIsResident) PageStateInformation bit set always had the kPageIsLockedResident bit set even when they were not locked. With Mac OS 8.5, GetPageInformation returns a new PageStateInformation bit, kPageIsHeldResident. When Virtual Memory is on, kPageIsHeldResident indicates that a page is held in physical memory (but not necessarily locked) with HoldMemory, LockMemory or LockMemoryForOutput. Related Materials: The InterfaceLib and Virtual Memory Manager sections. Designing PCI Cards & Drivers

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