1.\" 2.\" Copyright (c) 2003 Robert N. M. Watson 3.\" All rights reserved. 4.\" 5.\" Redistribution and use in source and binary forms, with or without 6.\" modification, are permitted provided that the following conditions 7.\" are met: 8.\" 1. Redistributions of source code must retain the above copyright 9.\" notice(s), this list of conditions and the following disclaimer as 10.\" the first lines of this file unmodified other than the possible 11.\" addition of one or more copyright notices. 12.\" 2. Redistributions in binary form must reproduce the above copyright 13.\" notice(s), this list of conditions and the following disclaimer in the 14.\" documentation and/or other materials provided with the distribution. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY 17.\" EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED 18.\" WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE 19.\" DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE LIABLE FOR ANY 20.\" DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES 21.\" (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR 22.\" SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER 23.\" CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH 26.\" DAMAGE. 27.\" 28.\" $FreeBSD$ 29.\" 30.Dd February 18, 2004 31.Dt DISK 9 32.Os 33.Sh NAME 34.Nm disk 35.Nd kernel disk storage API 36.Sh SYNOPSIS 37.In geom/geom_disk.h 38.Ft struct *disk 39.Fn disk_alloc void 40.Ft void 41.Fn disk_create "struct disk *disk" "int version" 42.Ft void 43.Fn disk_destroy "struct disk *disk" 44.Sh DESCRIPTION 45The disk storage API permits kernel device drivers providing access to 46disk-like storage devices to advertise the device to other kernel 47components, including 48.Xr GEOM 4 49and 50.Xr devfs 5 . 51.Pp 52Each disk device is described by a 53.Vt "struct disk" 54structure, which contains a variety of parameters for the disk device, 55function pointers for various methods that may be performed on the device, 56as well as private data storage for the device driver. 57In addition, some fields are reserved for use by GEOM in managing access 58to the device and its statistics. 59.Pp 60GEOM has the ownership of 61.Vt "struct disk" , 62and drivers must allocate storage for it with the 63.Fn disk_alloc 64function, 65fill in the fields and call 66.Fn disk_create 67when the device is ready to service requests. 68After calling 69.Fn disk_destroy , 70the device driver is not allowed to access the contents of 71.Vt "struct disk" 72anymore. 73.Pp 74The 75.Fn disk_create 76function 77takes a second parameter, 78.Fa version , 79which must always be passed 80.Dv DISK_VERSION . 81If GEOM detects that the driver is compiled against an unsupported version, 82it will ignore the device and print a warning on the console. 83.Ss Descriptive Fields 84The following fields identify the disk device described by the structure 85instance, and must be filled in prior to submitting the structure to 86.Fn disk_create 87and may not be subsequently changed: 88.Bl -tag -width indent 89.It Vt u_int Va d_flags 90Optional flags indicating to the storage framework what optional features 91or descriptions the storage device driver supports. 92Currently supported flags are 93.Dv DISKFLAG_NEEDSGIANT 94(maintained by device driver), 95.Dv DISKFLAG_OPEN 96(maintained by storage framework), 97and 98.Dv DISKFLAG_CANDELETE 99(maintained by device driver). 100.It Vt "const char *" Va d_name 101Holds the name of the storage device class, e.g., 102.Dq Li ahd . 103This value typically uniquely identifies a particular driver device, 104and must not conflict with devices serviced by other device drivers. 105.It Vt u_int Va d_unit 106Holds the instance of the storage device class, e.g., 107.Dq Li 4 . 108This namespace is managed by the device driver, and assignment of unit 109numbers might be a property of probe order, or in some cases topology. 110Together, the 111.Va d_name 112and 113.Va d_unit 114values will uniquely identify a disk storage device. 115.El 116.Ss Disk Device Methods 117The following fields identify various disk device methods, if implemented: 118.Bl -tag -width indent 119.It Vt "disk_open_t *" Va d_open 120Optional: invoked when the disk device is opened. 121If no method is provided, open will always succeed. 122.It Vt "disk_close_t *" Va d_close 123Optional: invoked when the disk device is closed. 124Although an error code may be returned, the call should always terminate 125any state setup by the corresponding open method call. 126.It Vt "disk_strategy_t *" Va d_strategy 127Mandatory: invoked when a new 128.Vt "struct bio" 129is to be initiated on the disk device. 130.It Vt "disk_ioctl_t *" Va d_ioctl 131Optional: invoked when an I/O control operation is initiated on the disk device. 132Please note that for security reasons these operations should not 133be able to affect other devices than the one on which they are performed. 134.It Vt "dumper_t *" Va d_dump 135Optional: if configured with 136.Xr dumpon 8 , 137this function is invoked from a very restricted system state after a 138kernel panic to record a copy of the system RAM to the disk. 139.El 140.Ss Mandatory Media Properties 141The following fields identify the size and granularity of the disk device. 142These fields must stay stable from return of the drivers open method until 143the close method is called, but it is perfectly legal to modify them in 144the open method before returning. 145.Bl -tag -width indent 146.It Vt u_int Va d_sectorsize 147The sector size of the disk device in bytes. 148.It Vt off_t Va d_mediasize 149The size of the disk device in bytes. 150.It Vt u_int Va d_maxsize 151The maximum supported size in bytes of an I/O request. 152Requests larger than this size will be chopped up by GEOM. 153.El 154.Ss Optional Media Properties 155These optional fields can provide extra information about the disk 156device. 157Do not initialize these fields if the field/concept does not apply. 158These fields must stay stable from return of the drivers open method until 159the close method is called, but it is perfectly legal to modify them in 160the open method before returning. 161.Bl -tag -width indent 162.It Vt u_int Va d_fwsectors , Vt u_int Va d_fwheads 163The number of sectors and heads advertised on the disk device by the 164firmware or BIOS. 165These values are almost universally bogus, but on some architectures 166necessary for the correct calculation of disk partitioning. 167.It Vt u_int Va d_stripeoffset , Vt u_int Va d_stripesize 168These two fields can be used to describe the width and location of 169natural performance boundaries for most disk technologies. 170Please see 171.Pa src/sys/geom/notes 172for details. 173.El 174.Ss Driver Private Data 175This field may be used by the device driver to store a pointer to 176private data to implement the disk service. 177.Bl -tag -width indent 178.It Vt "void *" Va d_drv1 179Private data pointer. 180Typically used to store a pointer to the drivers 181.Vt softc 182structure for this disk device. 183.El 184.Sh SEE ALSO 185.Xr GEOM 4 , 186.Xr devfs 5 187.Sh AUTHORS 188This manual page was written by 189.An Robert Watson . 190