Kernel Functions for Drivers                     drvhztousec(9F)



NAME
     drvhztousec - convert clock ticks to microseconds

SYNOPSIS
     #include 
     #include 



     clockt drvhztousec(clockt hertz);


INTERFACE LEVEL
     Architecture independent level 1 (DI/DKI).

PARAMETERS
     hertz    The number of clock ticks to convert.


DESCRIPTION
     The drvhztousec() 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 ddigetlbolt(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. The drvhztousec() 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  parame-
     ter.   No  error  value  is  returned.  If  the  microsecond
     equivalent to hertz is too large  to  be  represented  as  a
     clockt, then the maximum clockt value will be returned.

CONTEXT
     The drvhztousec() function can be called from user,  inter-
     rupt, or kernel context.

SEE ALSO
     ddigetlbolt(9F), drvusectohz(9F), drvusecwait(9F)


     Writing Device Drivers







SunOS 5.11          Last change: 16 Jan 2006                    1