drv_usectohz man page on SmartOS

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       drv_usectohz - convert microseconds to clock ticks

       #include <sys/types.h>
       #include <sys/ddi.h>

       clock_t drv_usectohz(clock_t microsecs);

       Architecture independent level 1 (DDI/DKI).

		    The number of microseconds to convert.

       The  drv_usectohz()  function  converts	a  length of time expressed in
       microseconds to a number of system clock ticks. The time	 arguments  to
       timeout(9F) and delay(9F) are expressed in clock ticks.

       The drv_usectohz() function is a portable interface for drivers to make
       calls to timeout(9F) and delay(9F) and remain binary compatible	should
       the driver object file be used on a system with a different clock speed
       (a different number of ticks in a second).

       The value returned is the number of system clock	 ticks	equivalent  to
       the  microsecs  argument. No error value is returned. If the clock tick
       equivalent to microsecs is too large to be represented  as  a  clock_t,
       then the maximum clock_t value will be returned.

       The drv_usectohz() function can be called from user, interrupt, or ker‐
       nel context.

       delay(9F), drv_hztousec(9F), timeout(9F)

       Writing Device Drivers

       If  the	 microsecs   argument	to   drv_usectohz()   is   less	  than
       drv_hztousec(9F),  drv_usectohz()  returns one tick. This, coupled with
       multiplication, can  result  in	significantly  longer  durations  than
       expected.  For example, on a machine where hz is 100, calling drv_usec‐
       tohz() with a microsecs value less than 10000 returns a result  equiva‐
       lent to 10000 (1 tick). This type of mistake causes code such as"5000 *
       drv_usectohz(1000)" to compute a duration of 50 seconds instead of  the
       intended 5 seconds.

				 Apr 24, 2008		      DRV_USECTOHZ(9F)

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