DDI_INTR_GET_HILEVEL_PRI(9F) Kernel Functions for Drivers

NAME

ddi_intr_get_hilevel_pri - get minimum priority level for a high-level
interrupt

SYNOPSIS

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

int ddi_intr_get_hilevel_pri(void);

INTERFACE LEVEL

illumos DDI specific (illumos DDI).

DESCRIPTION

Upon a successful return, the ddi_intr_get_hilevel_pri() function returns
the minimum priority level for a high-level interrupt. The return
priority value can be used to compare to other priority values, such as
those returned from ddi_intr_get_pri(9F), to determine if a given
interrupt priority is a high-level interrupt.


High-level interrupts must be handled without using system services that
manipulate thread or process states, because such interrupts are not
blocked by the scheduler.


In addition, high-level interrupt handlers must take care to do a minimum
of work because they cannot be preempted.


A typical high-level interrupt handler puts data into a circular buffer
and schedule a soft interrupt by calling ddi_intr_trigger_softint(). The
circular buffer can be protected by using a mutex that is properly
initialized for the interrupt handler.


The ddi_intr_get_hilevel_pri() function can be used before calling
ddi_intr_add_handler() to help determine which type of interrupt handler
can be used. Most device drivers are designed with the knowledge that
supported devices always generate low level interrupts. On some machines,
however, interrupts are high-level above the scheduler level and on other
machines they are not. Devices such as those those using SBus interrupts
or VME bus level 6 or 7 interrupts must use the
ddi_intr_get_hilevel_pri() function to test the type of interrupt handler
that can be used.

RETURN VALUES

The ddi_intr_get_hilevel_pri() function returns the priority value for a
high-level interrupt.

CONTEXT

The ddi_intr_get_hilevel_pri() function can be called from either user or
kernel non-interrupt context.

ATTRIBUTES

See attributes(7) for descriptions of the following attributes:


+--------------------+-----------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+--------------------+-----------------+
|Interface Stability | Committed |
+--------------------+-----------------+

SEE ALSO

attributes(7), ddi_intr_add_handler(9F), ddi_intr_alloc(9F),
ddi_intr_enable(9F), ddi_intr_get_pri(9F), ddi_intr_trigger_softint(9F),
mutex(9F)


Writing Device Drivers


April 7, 2005 DDI_INTR_GET_HILEVEL_PRI(9F)