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35 .Nd kernel disk storage API
41 .Fn disk_create "struct disk *disk" "int version"
43 .Fn disk_gone "struct disk *disk"
45 .Fn disk_destroy "struct disk *disk"
47 .Fn disk_resize "struct disk *disk" "int flags"
49 The disk storage API permits kernel device drivers providing access to
50 disk-like storage devices to advertise the device to other kernel
56 Each disk device is described by a
58 structure, which contains a variety of parameters for the disk device,
59 function pointers for various methods that may be performed on the device,
60 as well as private data storage for the device driver.
61 In addition, some fields are reserved for use by GEOM in managing access
62 to the device and its statistics.
64 GEOM has the ownership of
66 and drivers must allocate storage for it with the
69 fill in the fields and call
71 when the device is ready to service requests.
73 can be called by the driver after modifying
75 to notify GEOM about the disk capacity change.
78 field should be set to either M_WAITOK, or M_NOWAIT.
80 orphans all of the providers associated with the drive, setting an error
81 condition of ENXIO in each one.
82 In addition, it prevents a re-taste on last close for writing if an error
83 condition has been set in the provider.
86 the device driver is not allowed to access the contents of
93 takes a second parameter,
95 which must always be passed
97 If GEOM detects that the driver is compiled against an unsupported version,
98 it will ignore the device and print a warning on the console.
99 .Ss Descriptive Fields
100 The following fields identify the disk device described by the structure
101 instance, and must be filled in prior to submitting the structure to
103 and may not be subsequently changed:
104 .Bl -tag -width indent
105 .It Vt u_int Va d_flags
106 Optional flags indicating to the storage framework what optional features
107 or descriptions the storage device driver supports.
108 Currently supported flags are
109 .Dv DISKFLAG_NEEDSGIANT
110 (maintained by device driver),
112 (maintained by storage framework),
113 .Dv DISKFLAG_CANDELETE
114 (maintained by device driver),
116 .Dv DISKFLAG_CANFLUSHCACHE
117 (maintained by device driver).
118 .It Vt "const char *" Va d_name
119 Holds the name of the storage device class, e.g.,
121 This value typically uniquely identifies a particular driver device,
122 and must not conflict with devices serviced by other device drivers.
123 .It Vt u_int Va d_unit
124 Holds the instance of the storage device class, e.g.,
126 This namespace is managed by the device driver, and assignment of unit
127 numbers might be a property of probe order, or in some cases topology.
132 values will uniquely identify a disk storage device.
134 .Ss Disk Device Methods
135 The following fields identify various disk device methods, if implemented:
136 .Bl -tag -width indent
137 .It Vt "disk_open_t *" Va d_open
138 Optional: invoked when the disk device is opened.
139 If no method is provided, open will always succeed.
140 .It Vt "disk_close_t *" Va d_close
141 Optional: invoked when the disk device is closed.
142 Although an error code may be returned, the call should always terminate
143 any state setup by the corresponding open method call.
144 .It Vt "disk_strategy_t *" Va d_strategy
145 Mandatory: invoked when a new
147 is to be initiated on the disk device.
148 .It Vt "disk_ioctl_t *" Va d_ioctl
149 Optional: invoked when an I/O control operation is initiated on the disk device.
150 Please note that for security reasons these operations should not
151 be able to affect other devices than the one on which they are performed.
152 .It Vt "dumper_t *" Va d_dump
153 Optional: if configured with
155 this function is invoked from a very restricted system state after a
156 kernel panic to record a copy of the system RAM to the disk.
157 .It Vt "disk_getattr_t *" Va d_getattr
158 Optional: if this method is provided, it gives the disk driver the
159 opportunity to override the default GEOM response to BIO_GETATTR requests.
160 This function should return -1 if the attribute is not handled, 0 if the
161 attribute is handled, or an errno to be passed to g_io_deliver().
162 .It Vt "disk_gone_t *" Va d_gone
163 Optional: if this method is provided, it will be called after disk_gone()
164 is called, once GEOM has finished its cleanup process.
165 Once this callback is called, it is safe for the disk driver to free all of
166 its resources, as it will not be receiving further calls from GEOM.
168 .Ss Mandatory Media Properties
169 The following fields identify the size and granularity of the disk device.
170 These fields must stay stable from return of the drivers open method until
171 the close method is called, but it is perfectly legal to modify them in
172 the open method before returning.
173 .Bl -tag -width indent
174 .It Vt u_int Va d_sectorsize
175 The sector size of the disk device in bytes.
176 .It Vt off_t Va d_mediasize
177 The size of the disk device in bytes.
178 .It Vt u_int Va d_maxsize
179 The maximum supported size in bytes of an I/O request.
180 Requests larger than this size will be chopped up by GEOM.
182 .Ss Optional Media Properties
183 These optional fields can provide extra information about the disk
185 Do not initialize these fields if the field/concept does not apply.
186 These fields must stay stable from return of the drivers open method until
187 the close method is called, but it is perfectly legal to modify them in
188 the open method before returning.
189 .Bl -tag -width indent
190 .It Vt u_int Va d_fwsectors , Vt u_int Va d_fwheads
191 The number of sectors and heads advertised on the disk device by the
193 These values are almost universally bogus, but on some architectures
194 necessary for the correct calculation of disk partitioning.
195 .It Vt u_int Va d_stripeoffset , Vt u_int Va d_stripesize
196 These two fields can be used to describe the width and location of
197 natural performance boundaries for most disk technologies.
199 .Pa src/sys/geom/notes
201 .It Vt char Va d_ident[DISK_IDENT_SIZE]
202 This field can and should be used to store disk's serial number if the
203 d_getattr method described above isn't implemented, or if it does not
204 support the GEOM::ident attribute.
205 .It Vt char Va d_descr[DISK_IDENT_SIZE]
206 This field can be used to store the disk vendor and product description.
207 .It Vt uint16_t Va d_hba_vendor
208 This field can be used to store the PCI vendor ID for the HBA connected to
210 .It Vt uint16_t Va d_hba_device
211 This field can be used to store the PCI device ID for the HBA connected to
213 .It Vt uint16_t Va d_hba_subvendor
214 This field can be used to store the PCI subvendor ID for the HBA connected to
216 .It Vt uint16_t Va d_hba_subdevice
217 This field can be used to store the PCI subdevice ID for the HBA connected to
220 .Ss Driver Private Data
221 This field may be used by the device driver to store a pointer to
222 private data to implement the disk service.
223 .Bl -tag -width indent
224 .It Vt "void *" Va d_drv1
225 Private data pointer.
226 Typically used to store a pointer to the drivers
228 structure for this disk device.
234 This manual page was written by