217 lines
6.6 KiB
Groff
217 lines
6.6 KiB
Groff
.\" Copyright (c) 2000 Jeroen Ruigrok van der Werven
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd November 3, 2010
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.Dt BUS_SETUP_INTR 9
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.Os
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.Sh NAME
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.Nm BUS_SETUP_INTR ,
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.Nm bus_setup_intr ,
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.Nm BUS_TEARDOWN_INTR ,
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.Nm bus_teardown_intr
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.Nd create, attach and teardown an interrupt handler
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.Sh SYNOPSIS
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.In sys/param.h
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.In sys/bus.h
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.Ft int
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.Fo BUS_SETUP_INTR
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.Fa "device_t dev" "device_t child" "struct resource *irq" "int flags"
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.Fa "driver_filter_t *filter" "driver_intr_t *ithread" "void *arg"
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.Fa "void **cookiep"
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.Fc
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.Ft int
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.Fo bus_setup_intr
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.Fa "device_t dev" "struct resource *r" "int flags"
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.Fa "driver_filter_t filter" "driver_intr_t ithread" "void *arg"
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.Fa "void **cookiep"
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.Fc
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.Ft int
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.Fo BUS_TEARDOWN_INTR
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.Fa "device_t dev" "device_t child" "struct resource *irq" "void *cookiep"
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.Fc
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.Ft int
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.Fn bus_teardown_intr "device_t dev" "struct resource *r" "void *cookiep"
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.Sh DESCRIPTION
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The
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.Fn BUS_SETUP_INTR
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method
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will create and attach an interrupt handler to an interrupt
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previously allocated by the resource manager's
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.Xr BUS_ALLOC_RESOURCE 9
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method.
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The
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.Fa flags
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are found in
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.In sys/bus.h ,
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and give the broad category of interrupt.
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The
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.Fa flags
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also tell the interrupt handlers about certain
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device driver characteristics.
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.Dv INTR_EXCL
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marks the handler as being
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an exclusive handler for this interrupt.
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.Dv INTR_MPSAFE
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tells the scheduler that the interrupt handler
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is well behaved in a preemptive environment
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(``SMP safe''),
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and does not need
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to be protected by the ``Giant Lock'' mutex.
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.Dv INTR_ENTROPY
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marks the interrupt as being a good source of entropy -
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this may be used by the entropy device
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.Pa /dev/random .
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.Pp
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To define a time-critical handler that will not execute any potentially
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blocking operation, use the
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.Fa filter
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argument.
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See the
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.Sx "Filter Routines"
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section below for information on writing a filter.
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Otherwise, use the
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.Fa ithread
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argument.
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The defined handler
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will be called with the value
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.Fa arg
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as its only argument.
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See the
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.Sx "ithread Routines"
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section below for more information on writing an interrupt handler.
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.Pp
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The
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.Fa cookiep
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argument is a pointer to a
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.Vt "void *"
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that
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.Fn BUS_SETUP_INTR
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will write a cookie for the parent bus' use to if it is successful in
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establishing an interrupt.
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Driver writers may assume that this cookie will be non-zero.
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The nexus driver will write 0 on failure to
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.Fa cookiep .
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.Pp
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The interrupt handler will be detached by
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.Fn BUS_TEARDOWN_INTR .
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The cookie needs to be passed to
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.Fn BUS_TEARDOWN_INTR
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in order to tear down the correct interrupt handler.
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Once
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.Fn BUS_TEARDOWN_INTR
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returns, it is guaranteed that the interrupt function is not active and
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will no longer be called.
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.Pp
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Mutexes are not allowed to be held across calls to these functions.
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.Ss "Filter Routines"
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A filter runs in primary interrupt context.
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In this context, normal mutexes cannot be used.
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Only the spin lock version of these can be used (specified by passing
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.Dv MTX_SPIN
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to
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.Fn mtx_init
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when initializing the mutex).
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.Xr wakeup 9
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and similar routines can be called.
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Atomic operations from
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.Pa machine/atomic
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may be used.
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Reads and writes to hardware through
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.Xr bus_space 9
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may be used.
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PCI configuration registers may be read and written.
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All other kernel interfaces cannot be used.
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.Pp
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In this restricted environment, care must be taken to account for all
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races.
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A careful analysis of races should be done as well.
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It is generally cheaper to take an extra interrupt, for example, than
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to protect variables with spinlocks.
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Read, modify, write cycles of hardware registers need to be carefully
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analyzed if other threads are accessing the same registers.
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.Pp
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Generally, a filter routine will use one of two strategies.
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The first strategy is to simply mask the interrupt in hardware and
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allow the
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.Dv ithread
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routine to read the state from the hardware and then reenable
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interrupts.
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The
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.Dv ithread
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also acknowledges the interrupt before re-enabling the interrupt
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source in hardware.
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Most PCI hardware can mask its interrupt source.
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.Pp
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The second common approach is to use a filter with multiple
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.Xr taskqueue 9
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tasks.
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In this case, the filter acknowledges the interrupts and queues the
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work to the appropriate taskqueue.
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Where one has to multiplex different kinds of interrupt sources, like
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a network card's transmit and receive paths, this can reduce lock
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contention and increase performance.
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.Pp
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You should not
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.Xr malloc 9
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from inside a filter.
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You may not call anything that uses a normal mutex.
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Witness may complain about these.
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.Ss "ithread Routines"
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You can do whatever you want in an ithread routine, except sleep.
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Care must be taken not to sleep in an ithread.
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In addition, one should minimize lock contention in an ithread routine
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because contested locks ripple over to all other ithread routines on
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that interrupt.
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.Ss "Sleeping"
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Sleeping is voluntarily giving up control of your thread.
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All the sleep routine found in
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.Xr msleep 9
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sleep.
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Waiting for a condition variable described in
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.Xr condvar 9
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is sleeping.
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Calling any function that does any of these things is sleeping.
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.Sh RETURN VALUES
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Zero is returned on success,
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otherwise an appropriate error is returned.
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.Sh SEE ALSO
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.Xr random 4 ,
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.Xr device 9 ,
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.Xr driver 9 ,
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.Xr locking 9
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.Sh AUTHORS
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.An -nosplit
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This manual page was written by
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.An Jeroen Ruigrok van der Werven
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.Aq asmodai@FreeBSD.org
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based on the manual pages for
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.Fn BUS_CREATE_INTR
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and
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.Fn BUS_CONNECT_INTR
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written by
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.An Doug Rabson
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.Aq dfr@FreeBSD.org .
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