NAME

drv_hztousec − convert clock ticks to microseconds

SYNOPSIS

#include <sys/types.h>
#include <sys/ddi.h>
clock_t drv_hztousec(clock_t hertz);

INTERFACE LEVEL

Architecture independent level 1 (DDI/DKI). 

ARGUMENTS

hertz The number of clock ticks to convert. 

DESCRIPTION

drv_hztousec() converts into microseconds the time expressed by hertz, which is in system clock ticks.

The kernel variable lbolt, which is (only) readable through drv_getparm(9F), is the length of time the system has been up since boot and is expressed in clock ticks.  Drivers often use the value of lbolt before and after an I/O request to measure the amount of time it took the device to process the request.  drv_hztousec() can be used by the driver to convert the reading from clock ticks to a known unit of time. 

RETURN VALUES

The number of microseconds equivalent to the hertz argument. 
No error value is returned. If the microsecond equivalent to hertz is too large to be represented as a clock_t , then the maximum clock_t value will be returned. 

CONTEXT

drv_hztousec() can be called from user or interrupt context. 

SEE ALSO

drv_getparm(9F), drv_usectohz(9F), drv_usecwait(9F)

Writing Device Drivers

SunOS 5.5/x86  —  Last change: 12 Nov 1992