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

     drv_hztousec() 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 sys-
     tem 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  parame-
     ter.   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

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

     Writing Device Drivers