sunos man page for ks_snapshot

ks_snapshot(9E) 														   ks_snapshot(9E)

NAME
       ks_snapshot - take a snapshot of kstat data

SYNOPSIS
       #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);

INTERFACE LEVEL
       Solaris DDI specific (Solaris DDI).

       ksp

	   Pointer to a kstat(9S) structure.

       buf

	   Pointer to a buffer to copy the snapshot into.

       rw

	   Read/Write flag. Possible values are:

	   KSTAT_READ

	       Copy driver statistics from the driver to the buffer.

	   KSTAT_WRITE

	       Copy statistics from the buffer to the driver.

       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:

       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);
       }

       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  consis-
       tent data) and will prevent the kstat from being removed.

       1.  ks_snaptime must be set (via gethrtime(9F)) to timestamp the data.

       2.  Data gets copied from the kstat to the buffer on KSTAT_READ, and from the buffer to the kstat on KSTAT_WRITE.

       0

	   Success

       EACCES

	   If KSTAT_WRITE is not allowed

       EIO

	   For any other error

       This function is called from user context only.

       Example 1: Named kstats with Long Strings (KSTAT_DATA_STRING)

       static int
       xxx_kstat_snapshot(kstat_t *ksp, void *buf, int rw)
       {
	   if (rw == KSTAT_WRITE) {
		return (EACCES);
	   } 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);
       }

       ks_update(9E), kstat_create(9F), kstat_install(9F), kstat(9S)

								    4 Dec 2002							   ks_snapshot(9E)