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Poul-Henning Kamp 2004-02-18 22:10:08 +00:00
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108
share/man/man9/disk.9
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@ -35,13 +35,13 @@
.Nd Kernel disk storage API .Nd Kernel disk storage API
.Sh SYNOPSIS .Sh SYNOPSIS
.In geom/geom_disk.h .In geom/geom_disk.h
.Ft struct *disk
.Fo disk_alloc
.Fc
.Ft void .Ft void
.Fo disk_create .Fo disk_create
.Fa "int unit"
.Fa "struct disk *disk" .Fa "struct disk *disk"
.Fa "int flags" .Fa "int version"
.Fa "void *unused"
.Fa "void *unused2"
.Fc .Fc
.Ft void .Ft void
.Fn disk_destroy "struct disk *disk" .Fn disk_destroy "struct disk *disk"
@ -60,33 +60,40 @@ function pointers for various methods that may be performed on the device,
as well as private data storage for the device driver. as well as private data storage for the device driver.
In addition, some fields are reserved for use by GEOM in managing access In addition, some fields are reserved for use by GEOM in managing access
to the device and its statistics. to the device and its statistics.
Because of storage driver framework private data stored in .Pp
GEOM has the ownership of
.Vt "struct disk" , .Vt "struct disk" ,
instances of the structure should be allocated out of writable, pre-zero'd and drivers must allocate storage for it with the
memory. .Fn disk_alloc
function,
fill in the fields and call
.Fn disk_create
when the device is ready to service requests.
After calling
.Fn disk_destroy
the device driver are not allowed to access the contents of struct disk
any more.
.Pp .Pp
Public fields in the structure will generally be assumed not to change once .Fn disk_create
the structure is submitted to takes a second parameter
.Fn disk_create , .Va version
and so no explicit locking is employed; drivers that change the values of which must always be passed
any of these fields do so at their own risk. .Dv DISK_VERSION .
If GEOM detects that the driver is compiled against an unsupported version
it will ignore the device and print a warning on the console.
.Pp .Pp
Memory associated with the
.Vt "struct disk"
is owned by the device driver, but should not be released until after
the completion of a call to
.Fn disk_destroy .
.Ss Descriptive Fields .Ss Descriptive Fields
.Pp .Pp
The following fields identify the disk device described by the structure The following fields identify the disk device described by the structure
instance, and must be filled in prior to submitting the structure to instance, and must be filled in prior to submitting the structure to
.Fn disk_create : .Fn disk_create
and may not be subsequently changed:
.Bl -tag -width XXX .Bl -tag -width XXX
.It Vt u_int Va d_flags .It Vt u_int Va d_flags
Optional flags indicating to the storage framework what optional features Optional flags indicating to the storage framework what optional features
or descriptions the storage device driver supports. or descriptions the storage device driver supports.
Currently supported flags are Currently supported flags are
.Dv DISKFLAG_NOGIANT .Dv DISKFLAG_NEEDSGIANT
(maintained by device driver), (maintained by device driver),
.Dv DISKFLAG_OPEN .Dv DISKFLAG_OPEN
(maintained by storage framework), (maintained by storage framework),
@ -114,40 +121,61 @@ values will uniquely identify a disk storage device.
The following fields identify various disk device methods, if implemented: The following fields identify various disk device methods, if implemented:
.Bl -tag -width XXX .Bl -tag -width XXX
.It Vt "disk_open_t *" Va d_open .It Vt "disk_open_t *" Va d_open
Invoked when the disk device is opened. Optional: Invoked when the disk device is opened.
If no method is provided open will always succeed.
.It Vt "disk_close_t *" Va d_close .It Vt "disk_close_t *" Va d_close
Invoked when the disk device is closed. Optional: Invoked when the disk device is closed.
Although an error code may be returned, the call should always terminate
any state setup by the corresponing open method call.
.It Vt "disk_strategy_t *" Va d_strategy .It Vt "disk_strategy_t *" Va d_strategy
Invoked when a new Mandatory: Invoked when a new
.Vt struct bio .Vt struct bio
is to be initiated on the disk device. is to be initiated on the disk device.
.It Vt "disk_ioctl_t *" Va d_ioctl .It Vt "disk_ioctl_t *" Va d_ioctl
Invoked when a I/O control operation is initiated on the disk device. Optional: Invoked when a I/O control operation is initiated on the disk device.
Please note that for security reasons these operations should not
be able to affect other devices than the one on which they are performed.
.It Vt "dumper_t *" Va d_dump .It Vt "dumper_t *" Va d_dump
Invoked when a kernel crash dump is performed on the disk device. Optional: If configured with
.Xr dumpon 8
this function is invoked from a very restricted system state after a
kernel panic to record a copy of the sytem RAM to the disk.
.El .El
.Ss Media Properties .Ss Mandatory Media Properties
The following fields identify the size, layout, and other media properties The following fields identify the size and granularity of the disk device.
of the disk device. These fields must stay stable from return of the drivers open method until
the close method is called, but it is perfectly legal to modify them in
the open method before returning.
.Bl -tag -width XXX .Bl -tag -width XXX
.It Vt u_int Va d_sectorsize .It Vt u_int Va d_sectorsize
The sectorsize of the disk device. The sectorsize of the disk device in bytes.
.It Vt off_t Va d_mediasize .It Vt off_t Va d_mediasize
The size of the disk device in bytes. The size of the disk device in bytes.
.It Vt u_int Va d_fwsectors
The number of sectors advertised on the disk device by the firmware or
BIOS.
.It Vt u_int Va d_fwheads
The number of heads advertised on the disk device by the firmeware or
BIOS.
.It Vt u_int Va d_maxsize .It Vt u_int Va d_maxsize
The maximum I/O request the disk device supports. The maximum supported size in bytes of I/O request.
Requests larger than this size will be chopped up by GEOM.
.El
.Ss Optional Media Properties
These optional fields can provide extra information about the disk
device.
Do not initialize these fields if the field/concept does not apply.
These fields must stay stable from return of the drivers open method until
the close method is called, but it is perfectly legal to modify them in
the open method before returning.
.Bl -tag -width XXX
.It Vt u_int Va d_fwsectors
.It Vt u_int Va d_fwheads
The number of sectors and heads advertised on the disk device by the
firmware or BIOS.
These values are almost universally bogus, but on some architectures
necessary for the correct calculation of diskpartitioning.
.It Vt u_int Va d_stripeoffset .It Vt u_int Va d_stripeoffset
If the disk device supports an optimal stripe size and offset, such as
a RAID device, it may advertise that offset using this field.
.It Vt u_int Va d_stripesize .It Vt u_int Va d_stripesize
If the disk device supports an optimal stripe size and offset, such as These two fields can be used to describe the width and location of
a RAID device, it may advertise that size using this field. natural performance boundaries for most disk technologies.
Please see
.Xr src/sys/geom/notes
for details.
.El .El
.Ss Driver Private Data .Ss Driver Private Data
This field may be used by the device driver to store a pointer to This field may be used by the device driver to store a pointer to
@ -155,6 +183,8 @@ private data to implement the disk service.
.Bl -tag -width XXX .Bl -tag -width XXX
.It Vt "void *" Va d_drv1 .It Vt "void *" Va d_drv1
Private data pointer. Private data pointer.
Typically used to store a pointer to the drivers "softc" structure
for this disk device.
.El .El
.Sh SEE ALSO .Sh SEE ALSO
.Xr GEOM 4 , .Xr GEOM 4 ,