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.\" --(license Id: LICENSE.proto,v 1.1 2000/06/13 21:40:26 cgd Exp )--
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.Dd May 30, 2000
.Dt SOFTINTR 9
.Os
.Sh NAME
.Nm softintr ,
.Nm softintr_establish ,
.Nm softintr_disestablish ,
.Nm softintr_schedule
.Nd machine-independent software interrupt framework
.Sh SYNOPSIS
.Fd #include \*[Lt]machine/intr.h\*[Gt]
.Ft void *
.Fn softintr_establish "int level" "void (*fun)(void *)" "void *arg"
.Ft void
.Fn softintr_disestablish "void *cookie"
.Ft void
.Fn softintr_schedule "void *cookie"
.Sh DESCRIPTION
The
.Nx
machine-independent software interrupt framework is designed to provide
a generic software interrupt mechanism which can be used any time a
low-priority callback is needed.
It allows dynamic registration of software interrupts for loadable
drivers and protocol stacks, prioritization and fair queueing of software
interrupts, and allows machine-dependent optimizations to reduce cost
and code complexity.
.Pp
In order to provide this framework, the machine-dependent
.Aq Pa machine/types.h
must define the
.Dv __HAVE_GENERIC_SOFT_INTERRUPTS
symbol (without a value),
furthermore, the machine-dependent
.Aq Pa machine/intr.h
include file must provide prototypes for the
.Nm
functions and must provide definitions of
several constants which define software interrupt priority levels
(IPLs):
.Bl -tag -width "IPL_SOFTSERIAL"
.It Dv IPL_SOFTCLOCK
The software IPL for software clock interrupts
.Pq i.e., Fn softclock .
.It Dv IPL_SOFTNET
The software IPL for network callbacks.
.It Dv IPL_SOFTSERIAL
The software IPL for serial driver callbacks.
.El
.Pp
Other constants of the form
.Dv IPL_SOFT*
are reserved for future use by this framework.
.Pp
The following is a brief description of each function in the framework:
.Bl -tag -width "softintr_disestablish()"
.It Fn softintr_establish
Register a software interrupt at level
.Fa level ,
which will call the function
.Fa fun
with one
argument,
.Fa arg .
It may allocate a machine-specific data structure.
If successful,
.Fn softintr_establish
returns a
.Pf non- Dv NULL
opaque cookie which can be used as an argument to
.Fn softintr_schedule
or
.Fn softintr_disestablish .
If for some reason it does not succeed, it returns
.Dv NULL .
.It Fn softintr_disestablish
Deallocate a software interrupt previously allocated
by a call to
.Fn softintr_establish .
.\" XXX What happens to pending scheduled calls?
.It Fn softintr_schedule
Schedule a software interrupt previously allocated
by a call to
.Fn softintr_establish
to be executed as soon as that software interrupt is unblocked.
This function may assume that the interrupt is currently blocked,
so it need not check to see if the interrupt needs to be executed
immediately.
.Fn softintr_schedule
can safely be called multiple times before the
callback routine is invoked.
.El
.Sh SEE ALSO
.Xr spl 9
.Sh HISTORY
The
.Nx
machine-independent software interrupt framework was designed in 1997
and was implemented by one port in
.Nx 1.3 .
However, it did not gain wider implementation until
.Nx 1.5 .
.Sh AUTHORS
The
.Nx
machine-independent software interrupt framework was designed by
Charles Hannum \*[Lt]mycroft@NetBSD.ORG\*[Gt].