Tribblix: manual page: kstat

KSTAT_CREATE(9F) Kernel Functions for Drivers KSTAT_CREATE(9F)

NAME

kstat_create - create and initialize a new kstat

SYNOPSIS

#include <sys/types.h>
#include <sys/kstat.h>

kstat_t *kstat_create(const char *ks_module, int ks_instance,
const char *ks_name, const char *ks_class, uchar_t ks_type,
ulong_t ks_ndata, uchar_t ks_flag);

INTERFACE LEVEL

illumos DDI specific (illumos DDI)

PARAMETERS

ks_module
The name of the provider's module (such as "sd",
"esp", ...). The "core" kernel uses the name "unix".

ks_instance
The provider's instance number, as from
ddi_get_instance(9F). Modules which do not have a
meaningful instance number should use 0.

ks_name
A pointer to a string that uniquely identifies this
structure. Only KSTAT_STRLEN - 1 characters are
significant.

ks_class
The general class that this kstat belongs to. The
following classes are currently in use: disk, tape,
net, controller, vm, kvm, hat, streams, kstat, and
misc.

ks_type
The type of kstat to allocate. Valid types are:

KSTAT_TYPE_RAW
Raw data; allows more than one
data record per kstat.

KSTAT_TYPE_NAMED
Name=value pairs; allows more than
one data record per kstat.

KSTAT_TYPE_INTR
Interrupt; only one data record
per kstat.

KSTAT_TYPE_IO
I/O; only one data record per
kstat.

KSTAT_TYPE_TIMER
Event timer statistics; allows
more than one data record per
kstat.

ks_ndata
The number of type-specific data records to allocate.

ks_flag
A bit-field of various flags for this kstat. ks_flag
is some combination of:

KSTAT_FLAG_VIRTUAL
Tells kstat_create() not to
allocate memory for the kstat
data section; instead, the
driver will set the ks_data
field to point to the data it
wishes to export. This
provides a convenient way to
export existing data
structures.

KSTAT_FLAG_WRITABLE
Makes the kstat data section
writable by root.

KSTAT_FLAG_PERSISTENT
Indicates that this kstat is
to be persistent over time.
For persistent kstats,
kstat_delete(9F) simply marks
the kstat as dormant; a
subsequent kstat_create()
reactivates the kstat. This
feature is provided so that
statistics are not lost
across driver close/open
(such as raw disk I/O on a
disk with no mounted
partitions.) Note: Persistent
kstats cannot be virtual,
since ks_data points to
garbage as soon as the driver
goes away.

DESCRIPTION

kstat_create() is used in conjunction with kstat_install(9F) to
allocate and initialize a kstat(9S) structure. The method is
generally as follows:

kstat_create() allocates and performs necessary system initialization
of a kstat(9S) structure. kstat_create() allocates memory for the
entire kstat (header plus data), initializes all header fields,
initializes the data section to all zeroes, assigns a unique kstat ID
(KID), and puts the kstat onto the system's kstat chain. The returned
kstat is marked invalid because the provider (caller) has not yet had
a chance to initialize the data section.

After a successful call to kstat_create() the driver must perform any
necessary initialization of the data section (such as setting the
name fields in a kstat of type KSTAT_TYPE_NAMED). Virtual kstats must
have the ks_data field set at this time. The provider may also set
the ks_update, ks_private, and ks_lock fields if necessary.

Once the kstat is completely initialized, kstat_install(9F) is used
to make the kstat accessible to the outside world.

RETURN VALUES

If successful, kstat_create() returns a pointer to the allocated
kstat. NULL is returned upon failure.

CONTEXT

kstat_create() can be called from user or kernel context.

EXAMPLES

Example 1: Allocating and Initializing a kstat Structure

pkstat_t *ksp;
ksp = kstat_create(module, instance, name, class, type, ndata, flags);
if (ksp) {
/* ... provider initialization, if necessary */
kstat_install(ksp);
}