1.\" $NetBSD: devsw_attach.9,v 1.2 2015/05/14 13:59:15 wiz Exp $ 2.\" 3.\" Copyright (c) 2015 The NetBSD Foundation, Inc. 4.\" All rights reserved. 5.\" 6.\" This code is derived from software contributed to The NetBSD Foundation 7.\" by Kamil Rytarowski. 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 NETBSD FOUNDATION, INC. AND CONTRIBUTORS 19.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 20.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 21.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 22.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 23.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 24.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 25.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 26.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 27.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 28.\" POSSIBILITY OF SUCH DAMAGE. 29.\" 30.Dd May 13, 2015 31.Dt DEVSW_ATTACH 9 32.Os 33.Sh NAME 34.Nm devsw_attach , 35.Nm devsw_detach , 36.Nm bdevsw_lookup , 37.Nm cdevsw_lookup , 38.Nm bdevsw_lookup_major , 39.Nm cdevsw_lookup_major 40.Nd character and block device switch functions 41.Sh SYNOPSIS 42.In sys/conf.h 43.Ft int 44.Fo devsw_attach 45.Fa "const char *devname" 46.Fa "const struct bdevsw *bev" 47.Fa "devmajor_t *bmajor" 48.Fa "const struct cdevsw *cdev" 49.Fa "devmajor_t *cmajor" 50.Fc 51.Ft int 52.Fo devsw_detach 53.Fa "const struct bdevsw *bdev" 54.Fa "const struct cdevsw *cdev" 55.Fc 56.Ft "const struct bdevsw *" 57.Fo bdevsw_lookup 58.Fa "dev_t dev" 59.Fc 60.Ft "const struct cdevsw *" 61.Fo cdevsw_lookup 62.Fa "dev_t dev" 63.Fc 64.Ft devmajor_t 65.Fo bdevsw_lookup_major 66.Fa "const struct bdevsw *bdev" 67.Fc 68.Ft devmajor_t 69.Fo cdevsw_lookup_major 70.Fa "const struct cdevsw *cdev" 71.Fc 72.Sh DESCRIPTION 73If a device driver has character device interfaces accessed from 74userland, the driver must define a 75.Em cdevsw 76structure. 77If the driver also has block device interfaces, the driver must 78additionally define a 79.Em bdevsw 80structure. 81These structures are constant, and are defined within the 82.Xr driver 9 . 83.Pp 84For drivers which are included in the kernel via 85.Xr config 1 , 86the 87.Em cdevsw 88and 89.Em bdevsw 90structures are automatically linked into the configuration database. 91For drivers which are separately loaded, the 92.Fn devsw_attach 93function creates the necessary linkage and associates the 94.Em cdev 95and optional 96.Em bdev 97with the 98.Xr driver 9 . 99If there is no block device interface needed, 100.Em bdev 101should be set to 102.Dv NULL 103and 104.Em bmajor 105to 106.Dv \-1 . 107The 108.Em devname , 109major number, and device type 110(character or block) 111must correspond to the device file which will be opened by user programs. 112By passing 113.Dv \-1 114to the function for the 115.Em cmajor 116or 117.Em bmajor , 118the major number can be automatically generated. 119It can then be returned to userspace (for example, using 120.Xr sysctl 8 ) 121for creation of the device node. 122.Pp 123The 124.Fn devsw_detach 125function is used to detach the 126.Em bdev 127and 128.Em cdev 129structures. 130.Fn devsw_detach 131should be called before a loaded device driver is unloaded. 132.Pp 133The 134.Fn bdevsw_lookup 135and 136.Fn cdevsw_lookup 137functions return 138.Em "const struct bdevsw *" 139and 140.Em "const struct cdevsw *" 141for the given 142.Em dev . 143.Pp 144The 145.Fn bdevsw_lookup_major 146and 147.Fn cdevsw_lookup_major 148functions return 149.Em "devmajor_t" 150for the given 151.Em "const struct bdevsw *" 152or 153.Em "const struct cdevsw *" . 154.Sh RETURN VALUES 155Upon successful completion, 156.Fn devsw_attach 157and 158.Fn devsw_detach 159return 0. 160Otherwise they return an error value. 161.Pp 162In case of failure, 163.Fn bdevsw_lookup 164and 165.Fn cdevsw_lookup 166return the 167.Dv NULL 168value. 169.Pp 170The 171.Fn bdevsw_lookup_major 172and 173.Fn cdevsw_lookup_major 174functions return 175.Dv NODEVMAJOR 176for an unsuccessful completion. 177.Sh SEE ALSO 178.Xr driver 9 179