84 lines
1.5 KiB
C
84 lines
1.5 KiB
C
|
/*++
|
|||
|
|
|
|||
|
|
Copyright (c) 1994 Microsoft Corporation
|
|||
|
|
|
|||
|
|
Module Name:
|
|||
|
|
|
|||
|
|
xxclock.c
|
|||
|
|
|
|||
|
|
Abstract:
|
|||
|
|
|
|||
|
|
|
|||
|
|
This module implements the function necesssary to change the clock
|
|||
|
|
interrupt rate.
|
|||
|
|
|
|||
|
|
Author:
|
|||
|
|
|
|||
|
|
David N. Cutler (davec) 7-Feb-1994
|
|||
|
|
|
|||
|
|
Environment:
|
|||
|
|
|
|||
|
|
Kernel mode only.
|
|||
|
|
|
|||
|
|
Revision History:
|
|||
|
|
|
|||
|
|
--*/
|
|||
|
|
|
|||
|
|
#include "halp.h"
|
|||
|
|
|
|||
|
|
//
|
|||
|
|
// Define global data used to communicate new clock rates to the clock
|
|||
|
|
// interrupt service routine.
|
|||
|
|
//
|
|||
|
|
|
|||
|
|
ULONG HalpCurrentTimeIncrement;
|
|||
|
|
ULONG HalpNextIntervalCount;
|
|||
|
|
ULONG HalpNextTimeIncrement;
|
|||
|
|
ULONG HalpNewTimeIncrement;
|
|||
|
|
|
|||
|
|
ULONG
|
|||
|
|
HalSetTimeIncrement (
|
|||
|
|
IN ULONG DesiredIncrement
|
|||
|
|
)
|
|||
|
|
|
|||
|
|
/*++
|
|||
|
|
|
|||
|
|
Routine Description:
|
|||
|
|
|
|||
|
|
This function is called to set the clock interrupt rate to the frequency
|
|||
|
|
required by the specified time increment value.
|
|||
|
|
|
|||
|
|
N.B. This function is only executed on the processor that keeps the
|
|||
|
|
system time.
|
|||
|
|
|
|||
|
|
Arguments:
|
|||
|
|
|
|||
|
|
DesiredIncrement - Supplies desired number of 100ns units between clock
|
|||
|
|
interrupts.
|
|||
|
|
|
|||
|
|
Return Value:
|
|||
|
|
|
|||
|
|
The actual time increment in 100ns units.
|
|||
|
|
|
|||
|
|
--*/
|
|||
|
|
|
|||
|
|
{
|
|||
|
|
|
|||
|
|
ULONG NewTimeIncrement;
|
|||
|
|
ULONG NextIntervalCount;
|
|||
|
|
KIRQL OldIrql;
|
|||
|
|
|
|||
|
|
//
|
|||
|
|
// Raise IRQL to the highest level, set the new clock interrupt
|
|||
|
|
// parameters, lower IRQl, and return the new time increment value.
|
|||
|
|
//
|
|||
|
|
|
|||
|
|
KeRaiseIrql(HIGH_LEVEL, &OldIrql);
|
|||
|
|
NextIntervalCount = DesiredIncrement / MINIMUM_INCREMENT;
|
|||
|
|
NewTimeIncrement = NextIntervalCount * MINIMUM_INCREMENT;
|
|||
|
|
HalpNextIntervalCount = NextIntervalCount;
|
|||
|
|
HalpNewTimeIncrement = NewTimeIncrement;
|
|||
|
|
KeLowerIrql(OldIrql);
|
|||
|
|
return NewTimeIncrement;
|
|||
|
|
}
|