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drv_usecwait(9f) [suse man page]

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

NAME
drv_usecwait - busy-wait for specified interval SYNOPSIS
#include <sys/types.h> #include <sys/ddi.h> void drv_usecwait(clock_t microsecs); INTERFACE LEVEL
Architecture independent level 1 (DDI/DKI). PARAMETERS
microsecs The number of microseconds to busy-wait. DESCRIPTION
drv_usecwait() gives drivers a means of busy-waiting for a specified microsecond count. The amount of time spent busy-waiting may be greater than the microsecond count but will minimally be the number of microseconds specified. delay(9F) can be used by a driver to delay for a specified number of system ticks, but it has two limitations. First, the granularity of the wait time is limited to one clock tick, which may be more time than is needed for the delay. Second, delay(9F) may only be invoked from user context and hence cannot be used at interrupt time or system initialization. Often, drivers need to delay for only a few microseconds, waiting for a write to a device register to be picked up by the device. In this case, even in user context, delay(9F) produces too long a wait period. CONTEXT
drv_usecwait() can be called from user or interrupt context. SEE ALSO
delay(9F), timeout(9F), untimeout(9F) Writing Device Drivers NOTES
The driver wastes processor time by making this call since drv_usecwait() does not block but simply busy-waits. The driver should only make calls to drv_usecwait() as needed, and only for as much time as needed. drv_usecwait() does not mask out interrupts. SunOS 5.10 12 Nov 1992 drv_usecwait(9F)

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

NAME
drv_usecwait - busy-wait for specified interval SYNOPSIS
#include <sys/types.h> #include <sys/ddi.h> void drv_usecwait(clock_t microsecs); INTERFACE LEVEL
Architecture independent level 1 (DDI/DKI). PARAMETERS
microsecs The number of microseconds to busy-wait. DESCRIPTION
drv_usecwait() gives drivers a means of busy-waiting for a specified microsecond count. The amount of time spent busy-waiting may be greater than the microsecond count but will minimally be the number of microseconds specified. delay(9F) can be used by a driver to delay for a specified number of system ticks, but it has two limitations. First, the granularity of the wait time is limited to one clock tick, which may be more time than is needed for the delay. Second, delay(9F) may only be invoked from user context and hence cannot be used at interrupt time or system initialization. Often, drivers need to delay for only a few microseconds, waiting for a write to a device register to be picked up by the device. In this case, even in user context, delay(9F) produces too long a wait period. CONTEXT
drv_usecwait() can be called from user or interrupt context. SEE ALSO
delay(9F), timeout(9F), untimeout(9F) Writing Device Drivers NOTES
The driver wastes processor time by making this call since drv_usecwait() does not block but simply busy-waits. The driver should only make calls to drv_usecwait() as needed, and only for as much time as needed. drv_usecwait() does not mask out interrupts. SunOS 5.10 12 Nov 1992 drv_usecwait(9F)
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