1.\" -*- nroff -*- 2.\" 3.\" Copyright (c) 1998 Doug Rabson 4.\" 5.\" All rights reserved. 6.\" 7.\" This program is free software. 8.\" 9.\" Redistribution and use in source and binary forms, with or without 10.\" modification, are permitted provided that the following conditions 11.\" are met: 12.\" 1. Redistributions of source code must retain the above copyright 13.\" notice, this list of conditions and the following disclaimer. 14.\" 2. Redistributions in binary form must reproduce the above copyright 15.\" notice, this list of conditions and the following disclaimer in the 16.\" documentation and/or other materials provided with the distribution. 17.\" 18.\" THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY EXPRESS OR 19.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 20.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 21.\" IN NO EVENT SHALL THE DEVELOPERS BE LIABLE FOR ANY DIRECT, INDIRECT, 22.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 23.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 24.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 25.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 26.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 27.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 28.\" 29.\" $FreeBSD$ 30.\" 31.Dd January 6, 2005 32.Dt DEVICE_PROBE 9 33.Os 34.Sh NAME 35.Nm DEVICE_PROBE 36.Nd probe for device existence 37.Sh SYNOPSIS 38.In sys/param.h 39.In sys/bus.h 40.Ft int 41.Fn DEVICE_PROBE "device_t dev" 42.Sh DESCRIPTION 43The 44.Fn DEVICE_PROBE 45method should probe to see if the device is present. 46It should return 0 if the device exists, 47.Er ENXIO 48if it cannot be found. 49If some other error happens during the probe (such as a memory 50allocation failure), an appropriate error code should be returned. 51For 52cases where more than one driver matches a device, a priority value can 53be returned. 54In this case, success codes are values less than or equal 55to zero with the highest value representing the best match. 56Failure 57codes are represented by positive values and the regular 58.Ux 59error 60codes should be used for the purpose. 61.Pp 62If a driver returns a success code which is less than zero, it must 63not assume that it will be the same driver which is attached to the 64device. 65In particular, it must not assume that any values stored in 66the softc structure will be available for its attach method and any 67resources allocated during probe must be released and re-allocated 68if the attach method is called. 69In addition it is an absolute requirement that the probe routine have 70no side effects whatsoever. 71The probe routine may be called more than once before the attach 72routine is called. 73.Pp 74If a success code of zero is 75returned, the driver can assume that it will be the one attached, but 76must not hold any resources when the probe routine returns. 77A driver may assume that the softc is preserved when it returns 78a success code of zero. 79.Sh RETURN VALUES 80A value equal to or less than zero indicates success, greater than 81zero indicates an error (errno). 82For values equal to or less than 83zero: zero indicates highest priority, no further probing is done; 84for a value less than zero, the lower the value the lower the 85priority, e.g.\& -100 indicates a lower priority than -50. 86.Sh SEE ALSO 87.Xr device 9 , 88.Xr DEVICE_ATTACH 9 , 89.Xr DEVICE_DETACH 9 , 90.Xr DEVICE_IDENTIFY 9 , 91.Xr DEVICE_SHUTDOWN 9 92.Sh AUTHORS 93This manual page was written by 94.An Doug Rabson . 95