1 .\" Copyright (c) 1998 Doug Rabson
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27 .\" $FreeBSD: src/share/man/man9/DEVICE_PROBE.9,v 1.4.2.6 2001/12/17 11:30:18 ru Exp $
28 .\" $DragonFly: src/share/man/man9/DEVICE_PROBE.9,v 1.5 2008/11/09 10:27:47 swildner Exp $
35 .Nd probe for device existence
40 .Fn DEVICE_PROBE "device_t dev"
42 This device method should probe to see if the device is present.
43 It should return 0 if the device exists,
45 if it cannot be found.
46 If some other error happens during the probe (such as a memory
47 allocation failure), an appropriate error code should be returned.
49 cases where more than one driver matches a device, a priority value can
50 be returned. In this case, success codes are values less than or equal
51 to zero with the highest value representing the best match. Failure
52 codes are represented by positive values and the regular unix error
53 codes should be used for the purpose.
55 If a driver returns a success code which is less than zero, it must
56 not assume that it will be the same driver which is attached to the
58 In particular, it must not assume that any values stored in
59 the softc structure will be available for its attach method and any
60 resources allocated during probe must be released and re-allocated
61 if the attach method is called.
62 If a success code of zero is
63 returned, the driver can assume that it will be the one attached.
65 Devices which implement busses should use this method to probe for
66 the existence of devices attached to the bus and add them as
68 If this is combined with the use of
69 .Xr bus_generic_attach 9
70 the child devices will be automatically probed and attached.
72 A value equal to or less than zero indicates success, greater than
73 zero indicates an error
75 For values equal to or less than
76 zero: zero indicates highest priority, no further probing is done;
77 for a value less than zero, the lower the value the lower the
78 priority, e.g. -100 indicates a lower priority than -50.
83 This man page was written by