Document sbuf_new_for_sysctl(9).

Pointed out by:	lstewart

2 files changed, 15 insertions, 1 deletions

diff --git a/share/man/man9/Makefile b/share/man/man9/Makefile
index 6366b1f3deb5..fdcb106bb1cc 100644
--- a/share/man/man9/Makefile
+++ b/share/man/man9/Makefile
@@ -1031,6 +1031,7 @@ MLINKS+=sbuf.9 sbuf_bcat.9 \
 	sbuf.9 sbuf_finish.9 \
 	sbuf.9 sbuf_len.9 \
 	sbuf.9 sbuf_new.9 \
+	sbuf.9 sbuf_new_for_sysctl.9 \
 	sbuf.9 sbuf_printf.9 \
 	sbuf.9 sbuf_putc.9 \
 	sbuf.9 sbuf_set_drain.9 \
diff --git a/share/man/man9/sbuf.9 b/share/man/man9/sbuf.9
index 0b6aa908d079..798b1c890ffb 100644
--- a/share/man/man9/sbuf.9
+++ b/share/man/man9/sbuf.9
@@ -25,13 +25,14 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd May 17, 2009
+.Dd January 25, 2011
 .Dt SBUF 9
 .Os
 .Sh NAME
 .Nm sbuf ,
 .Nm sbuf_new ,
 .Nm sbuf_new_auto ,
+.Nm sbuf_new_for_sysctl ,
 .Nm sbuf_clear ,
 .Nm sbuf_setpos ,
 .Nm sbuf_bcat ,
@@ -99,6 +100,9 @@
 .Fn sbuf_done "struct sbuf *s"
 .Ft void
 .Fn sbuf_delete "struct sbuf *s"
+.In sys/sysctl.h
+.Ft struct sbuf *
+.Fn sbuf_new_for_sysctl "struct sbuf *s" "char *buf" "int length" "struct sysctl_req *req"
 .Sh DESCRIPTION
 The
 .Nm
@@ -169,6 +173,15 @@ and
 .Dv SBUF_AUTOEXTEND .
 .Pp
 The
+.Fn sbuf_new_for_sysctl
+function will set up an sbuf with a drain function to use
+.Fn SYSCTL_OUT
+when the internal buffer fills.
+The sysctl old buffer will be wired, which allows for doing an
+.Fn sbuf_printf
+while holding a mutex.
+.Pp
+The
 .Fn sbuf_delete
 function clears the
 .Fa sbuf