11544 ofmt(3OFMT) should talk about the callback handler
Reviewed by: Dan McDonald <danmcd@joyent.com>
Reviewed by: Jason King <jason.brian.king@gmail.com>

*** 9,20 ****
  .\" http://www.illumos.org/license/CDDL.
  .\"
  .\"
  .\" Copyright 2010 Sun Microsystems, Inc.  All rights reserved.
  .\" Copyright 2017 Nexenta Systems, Inc.
  .\"
! .Dd June 1, 2017
  .Dt OFMT 3OFMT
  .Os
  .Sh NAME
  .Nm ofmt_open ,
  .Nm ofmt_print ,
--- 9,21 ----
  .\" http://www.illumos.org/license/CDDL.
  .\"
  .\"
  .\" Copyright 2010 Sun Microsystems, Inc.  All rights reserved.
  .\" Copyright 2017 Nexenta Systems, Inc.
+ .\" Copyright 2018 Joyent, Inc.
  .\"
! .Dd December 20, 2018
  .Dt OFMT 3OFMT
  .Os
  .Sh NAME
  .Nm ofmt_open ,
  .Nm ofmt_print ,
*** 156,168 ****
  .Pp
  .Va of_cb
  is the application-specified callback function with the following prototype that
  provides a string representation of the value to be printed for the field:
  .Bd -literal -offset indent
! (*of_cb)(ofmt_arg_t *ofmt_arg, char *buf, uint_t bufsize)
  .Ed
  .Pp
  The interpretation of the
  .Va of_id
  field is completely private to the caller, and can be optionally used by the
  callback function as a cookie to identify the field being printed when a single
  callback function is shared between multiple
--- 157,181 ----
  .Pp
  .Va of_cb
  is the application-specified callback function with the following prototype that
  provides a string representation of the value to be printed for the field:
  .Bd -literal -offset indent
! boolean_t (*of_cb)(ofmt_arg_t *ofmt_arg, char *buf, uint_t bufsize)
  .Ed
  .Pp
+ The callback must not write beyond
+ .Fa bufsize
+ bytes of the string form into
+ .Fa buf .
+ If the function successfully translates the field into its string
+ representation and places it into
+ .Fa buf ,
+ then the callback function should return
+ .Dv B_TRUE .
+ Otherwise, the callback function should return
+ .Dv B_FALSE .
+ .Pp
  The interpretation of the
  .Va of_id
  field is completely private to the caller, and can be optionally used by the
  callback function as a cookie to identify the field being printed when a single
  callback function is shared between multiple