1.\" Copyright (c) 2000 Jeroen Ruigrok van der Werven 2.\" All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 13.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 14.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 15.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 16.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 17.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 18.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 19.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 20.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 21.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 22.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 23.\" SUCH DAMAGE. 24.\" 25.\" $FreeBSD$ 26.\" 27.Dd November 3, 2010 28.Dt BUS_SETUP_INTR 9 29.Os 30.Sh NAME 31.Nm BUS_SETUP_INTR , 32.Nm bus_setup_intr , 33.Nm BUS_TEARDOWN_INTR , 34.Nm bus_teardown_intr 35.Nd create, attach and teardown an interrupt handler 36.Sh SYNOPSIS 37.In sys/param.h 38.In sys/bus.h 39.Ft int 40.Fo BUS_SETUP_INTR 41.Fa "device_t dev" "device_t child" "struct resource *irq" "int flags" 42.Fa "driver_filter_t *filter" "driver_intr_t *ithread" "void *arg" 43.Fa "void **cookiep" 44.Fc 45.Ft int 46.Fo bus_setup_intr 47.Fa "device_t dev" "struct resource *r" "int flags" 48.Fa "driver_filter_t filter" "driver_intr_t ithread" "void *arg" 49.Fa "void **cookiep" 50.Fc 51.Ft int 52.Fo BUS_TEARDOWN_INTR 53.Fa "device_t dev" "device_t child" "struct resource *irq" "void *cookiep" 54.Fc 55.Ft int 56.Fn bus_teardown_intr "device_t dev" "struct resource *r" "void *cookiep" 57.Sh DESCRIPTION 58The 59.Fn BUS_SETUP_INTR 60method 61will create and attach an interrupt handler to an interrupt 62previously allocated by the resource manager's 63.Xr BUS_ALLOC_RESOURCE 9 64method. 65The 66.Fa flags 67are found in 68.In sys/bus.h , 69and give the broad category of interrupt. 70The 71.Fa flags 72also tell the interrupt handlers about certain 73device driver characteristics. 74.Dv INTR_EXCL 75marks the handler as being 76an exclusive handler for this interrupt. 77.Dv INTR_MPSAFE 78tells the scheduler that the interrupt handler 79is well behaved in a preemptive environment 80(``SMP safe''), 81and does not need 82to be protected by the ``Giant Lock'' mutex. 83.Dv INTR_ENTROPY 84marks the interrupt as being a good source of entropy - 85this may be used by the entropy device 86.Pa /dev/random . 87.Pp 88To define a time-critical handler that will not execute any potentially 89blocking operation, use the 90.Fa filter 91argument. 92See the 93.Sx "Filter Routines" 94section below for information on writing a filter. 95Otherwise, use the 96.Fa ithread 97argument. 98The defined handler 99will be called with the value 100.Fa arg 101as its only argument. 102See the 103.Sx "ithread Routines" 104section below for more information on writing an interrupt handler. 105.Pp 106The 107.Fa cookiep 108argument is a pointer to a 109.Vt "void *" 110that 111.Fn BUS_SETUP_INTR 112will write a cookie for the parent bus' use to if it is successful in 113establishing an interrupt. 114Driver writers may assume that this cookie will be non-zero. 115The nexus driver will write 0 on failure to 116.Fa cookiep . 117.Pp 118The interrupt handler will be detached by 119.Fn BUS_TEARDOWN_INTR . 120The cookie needs to be passed to 121.Fn BUS_TEARDOWN_INTR 122in order to tear down the correct interrupt handler. 123Once 124.Fn BUS_TEARDOWN_INTR 125returns, it is guaranteed that the interrupt function is not active and 126will no longer be called. 127.Pp 128Mutexes are not allowed to be held across calls to these functions. 129.Ss "Filter Routines" 130A filter runs in primary interrupt context. 131In this context, normal mutexes cannot be used. 132Only the spin lock version of these can be used (specified by passing 133.Dv MTX_SPIN 134to 135.Fn mtx_init 136when initializing the mutex). 137.Xr wakeup 9 138and similar routines can be called. 139Atomic operations from 140.Pa machine/atomic 141may be used. 142Reads and writes to hardware through 143.Xr bus_space 9 144may be used. 145PCI configuration registers may be read and written. 146All other kernel interfaces cannot be used. 147.Pp 148In this restricted environment, care must be taken to account for all 149races. 150A careful analysis of races should be done as well. 151It is generally cheaper to take an extra interrupt, for example, than 152to protect variables with spinlocks. 153Read, modify, write cycles of hardware registers need to be carefully 154analyzed if other threads are accessing the same registers. 155.Pp 156Generally, a filter routine will use one of two strategies. 157The first strategy is to simply mask the interrupt in hardware and 158allow the 159.Dv ithread 160routine to read the state from the hardware and then reenable 161interrupts. 162The 163.Dv ithread 164also acknowledges the interrupt before re-enabling the interrupt 165source in hardware. 166Most PCI hardware can mask its interrupt source. 167.Pp 168The second common approach is to use a filter with multiple 169.Xr taskqueue 9 170tasks. 171In this case, the filter acknowledges the interrupts and queues the 172work to the appropriate taskqueue. 173Where one has to multiplex different kinds of interrupt sources, like 174a network card's transmit and receive paths, this can reduce lock 175contention and increase performance. 176.Pp 177You should not 178.Xr malloc 9 179from inside a filter. 180You may not call anything that uses a normal mutex. 181Witness may complain about these. 182.Ss "ithread Routines" 183You can do whatever you want in an ithread routine, except sleep. 184Care must be taken not to sleep in an ithread. 185In addition, one should minimize lock contention in an ithread routine 186because contested locks ripple over to all other ithread routines on 187that interrupt. 188.Ss "Sleeping" 189Sleeping is voluntarily giving up control of your thread. 190All the sleep routine found in 191.Xr msleep 9 192sleep. 193Waiting for a condition variable described in 194.Xr condvar 9 195is sleeping. 196Calling any function that does any of these things is sleeping. 197.Sh RETURN VALUES 198Zero is returned on success, 199otherwise an appropriate error is returned. 200.Sh SEE ALSO 201.Xr random 4 , 202.Xr device 9 , 203.Xr driver 9 , 204.Xr locking 9 205.Sh AUTHORS 206.An -nosplit 207This manual page was written by 208.An Jeroen Ruigrok van der Werven 209.Aq asmodai@FreeBSD.org 210based on the manual pages for 211.Fn BUS_CREATE_INTR 212and 213.Fn BUS_CONNECT_INTR 214written by 215.An Doug Rabson 216.Aq dfr@FreeBSD.org . 217