DRV_USECTOHZ(9F)DRV_USECTOHZ(9F)NAMEdrv_usectohz - convert microseconds to clock ticks
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‐
SEE ALSOdelay(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)