DRV_HZTOUSEC(9F) Kernel Functions for Drivers DRV_HZTOUSEC(9F)

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).

PARAMETERS

hertz
The number of clock ticks to convert.

DESCRIPTION

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


The kernel variable lbolt, whose value should be retrieved by calling
ddi_get_lbolt(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. The drv_hztousec()
function 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 parameter. 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

The drv_hztousec() function can be called from user, interrupt, or
kernel context.

SEE ALSO

ddi_get_lbolt(9F), drv_usectohz(9F), drv_usecwait(9F)


Writing Device Drivers

January 16, 2006 DRV_HZTOUSEC(9F)