Copyright (c) 1994, Sun Microsystems, Inc., All Rights Reserved
The contents of this file are subject to the terms of the Common Development and Distribution License (the "License"). You may not use this file except in compliance with the License.
You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE or http://www.opensolaris.org/os/licensing. See the License for the specific language governing permissions and limitations under the License.
When distributing Covered Code, include this CDDL HEADER in each file and include the License file at usr/src/OPENSOLARIS.LICENSE. If applicable, add the following below this CDDL HEADER, with the fields enclosed by brackets "[]" replaced with your own identifying information: Portions Copyright [yyyy] [name of copyright owner]
#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);
Solaris DDI specific (Solaris DDI)
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.
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 consistent data) and will prevent the kstat from being removed.
ks_update() should return
0
For success.
EACCES
If KSTAT_WRITE is not allowed.
EIO
For any other error.
kstat_create(9F), kstat_install(9F), kstat(9S)
Writing Device Drivers