NetBSD/share/man/man9/softintr.9

.\" $NetBSD: softintr.9,v 1.2 2000/06/02 22:12:11 matt Exp $
.\"
.\" Copyright (c) 2000 Christopher G. Demetriou.
.\" All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\" 3. All advertising materials mentioning features or use of this software
.\"    must display the following acknowledgement:
.\"	This product includes software developed for the NetBSD Project
.\"	by Christopher G. Demetriou.
.\" 4. The name of the author may not be used to endorse or promote products
.\"    derived from this software without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
.\" BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
.\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
.\" AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
.\" OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.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 <machine/intr.h>
.Ft void *
.Fn softintr_establish "int level" "int (*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/intr.h
include file must provide prototypes for the
.Nm
functions, must define the
.Dv __GENERIC_SOFT_INTERRUPTS
symbol (without a value), 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 AUTHOR
The
.Nx
machine-independent software interrupt framework was designed by
Charles Hannum <mycroft@NetBSD.ORG>.
.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 .