ks_update(9E) Driver Entry Points ks_update(9E)NAME
ks_update - dynamically update kstats
SYNOPSIS
#include <sys/types.h>
#include <sys/kstat.h>
#include <sys/ddi.h>
#include <sys/sunddi.h>
int prefix_ks_update(kstat_t *ksp, int rw);
INTERFACE LEVEL
Solaris DDI specific (Solaris DDI)
PARAMETERS
ksp Pointer to a kstat(9S) structure.
rw Read/Write flag. Possible values are
KSTAT_READ Update kstat structure statistics from the driver.
KSTAT_WRITE Update driver statistics from the kstat structure.
DESCRIPTION
The kstat mechanism allows for an optional ks_update() function to update kstat data. This is useful for drivers where the underlying
device keeps cheap hardware statistics, but extraction is expensive. Instead of constantly keeping the kstat data section up to date, the
driver can supply a ks_update() function which updates the kstat's data section on demand. To take advantage of this feature, set the
ks_update field before calling kstat_install(9F).
The ks_update() function must have the following structure:
static int
xx_kstat_update(kstat_t *ksp, int rw)
{
if (rw == KSTAT_WRITE) {
/* update the native stats from ksp->ks_data */
/* return EACCES if you don't support this */
} else {
/* update ksp->ks_data from the native stats */
}
return(0);
}
In general, the ks_update() routine may need to refer to provider-private data; for example, it may need a pointer to the provider's raw
statistics. The ks_private field is available for this purpose. Its use is entirely at the provider's discretion.
No kstat locking should be done inside the ks_update() routine. The caller will already be holding the kstat's ks_lock (to ensure consis-
tent data) and will prevent the kstat from being removed.
RETURN VALUES
ks_update() should return
0 For success.
EACCES If KSTAT_WRITE is not allowed.
EIO For any other error.
SEE ALSO kstat_create(9F), kstat_install(9F), kstat(9S)
Writing Device Drivers
SunOS 5.11 27 May 1994 ks_update(9E)
Check Out this Related Man Page
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(char *module, int instance, char *name, char *class, uchar_t type, ulong_t ndata, uchar_t ks_flag);
INTERFACE LEVEL
Solaris DDI specific (Solaris DDI)
PARAMETERS
module The name of the provider's module (such as "sd", "esp", ...). The "core" kernel uses the name "unix".
instance The provider's instance number, as from ddi_get_instance(9F). Modules which do not have a meaningful instance number should
use 0.
name A pointer to a string that uniquely identifies this structure. Only KSTAT_STRLEN - 1 characters are significant.
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.
type The type of kstat to allocate. Valid types are:
"small and bold">KSTAT_TYPE_NAMED
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
ndata The number of type-specific data records to allocate.
flag A bit-field of various flags for this kstat. 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);
}
SEE ALSO kstat(3KSTAT), ddi_get_instance(9F), kstat_delete(9F), kstat_install(9F), kstat_named_init(9F), kstat(9S), kstat_named(9S)
Writing Device Drivers
SunOS 5.10 10 Sep 1994 kstat_create(9F)