Manual Pages for UNIX Operating System command usage for man ks_update

Driver Entry Points                                 ks_update(9E)



NAME
     ks_update - dynamically update kstats

SYNOPSIS
     #include 
     #include 
     #include 
     #include 



     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() func-
     tion 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 {



SunOS 5.11          Last change: 27 May 1994                    1






Driver Entry Points                                 ks_update(9E)



                 /* 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()  rou-
     tine.   The  caller  will  already  be  holding  the kstat's
     ks_lock (to ensure consistent 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          Last change: 27 May 1994                    2