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| Driver Entry Points | ks_snapshot(9E) |
| | ks_snapshot - take a snapshot of kstat data |
SYNOPSIS
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#include <sys/types.h>
#include <sys/kstat.h>
#include <sys/ddi.h>
#include <sys/sunddi.h>
int prefix_ks_snapshot(kstat_t *ksp, void *buf, int rw); |
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Solaris DDI specific (Solaris DDI).
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ksp
- Pointer to a kstat(9S) structure.
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buf
- Pointer to a buffer to copy the snapshot into.
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rw
- Read/Write flag. Possible values are:
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KSTAT_READ
- Copy driver statistics from the driver to the buffer.
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KSTAT_WRITE
- Copy statistics from the buffer to the driver.
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The kstat mechanism allows for an optional ks_snapshot() function to copy kstat data. This is the routine that is called to marshall the kstat data to be copied to user-land. A driver can opt to use a custom snapshot routine
rather than the default snapshot routine; to take advantage of this feature, set the ks_snapshot field before calling kstat_install(9F).
The ks_snapshot() function must have the following structure:
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static int
xx_kstat_snapshot(kstat_t *ksp, void *buf, int rw)
{
if (rw == KSTAT_WRITE) {
/* set the native stats to the values in buf */
/* return EACCES if you don't support this */
} else {
/* copy the kstat-specific data into buf */
}
return (0);
}
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In general, the ks_snapshot() routine might need to refer to provider-private data; for example, it might 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.
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ks_snaptime must be set (via gethrtime(9F)) to timestamp the data.
- Data gets copied from the kstat to the buffer on KSTAT_READ, and from the buffer to the kstat on KSTAT_WRITE.
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0
- Success
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EACCESS
- If KSTAT_WRITE is not allowed
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EIO
- For any other error
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This function is called from user context only.
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| | Example 1. Named kstats with Long Strings (KSTAT_DATA_STRING)
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static int
xxx_kstat_snapshot(kstat_t *ksp, void *buf, int rw)
{
if (rw == KSTAT_WRITE) {
return (EACCESS);
} else {
kstat_named_t *knp = buf;
char *end = knp + ksp->ks_ndata;
uint_t i;
bcopy(ksp->ks_data, buf,
sizeof (kstat_named_t) * ksp->ks_ndata);
/*
* Now copy the strings to the end of the buffer, and
* update the pointers appropriately.
*/
for (i = 0; i < ksp->ks_ndata; i++, knp++)
if (knp->data_type == KSTAT_DATA_STRING &&
KSTAT_NAMED_STR_PTR(knp) != NULL) {
bcopy(KSTAT_NAMED_STR_PTR(knp), end,
KSTAT_NAMED_STR_BUFLEN(knp));
KSTAT_NAMED_STR_PTR(knp) = end;
end += KSTAT_NAMED_STR_BUFLEN(knp);
}
}
return (0);
}
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