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From: Konstantin Belousov <kib@FreeBSD.org>
Date: Sun, 5 Sep 2010 14:47:46 +0000 (UTC)
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Subject: svn commit: r212233 - head/share/man/man9
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Author: kib
Date: Sun Sep  5 14:47:46 2010
New Revision: 212233
URL: http://svn.freebsd.org/changeset/base/212233

Log:
  Document MAKEDEV_ETERNAL.
  
  MFC after:	3 days

Modified:
  head/share/man/man9/make_dev.9

Modified: head/share/man/man9/make_dev.9
==============================================================================
--- head/share/man/man9/make_dev.9	Sun Sep  5 14:37:29 2010	(r212232)
+++ head/share/man/man9/make_dev.9	Sun Sep  5 14:47:46 2010	(r212233)
@@ -24,7 +24,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd May 6, 2010
+.Dd September 5, 2010
 .Dt MAKE_DEV 9
 .Os
 .Sh NAME
@@ -135,6 +135,7 @@ The following values are currently accep
 MAKEDEV_REF	reference the created device
 MAKEDEV_NOWAIT	do not sleep, may return NULL
 MAKEDEV_WAITOK	allow the function to sleep to satisfy malloc
+MAKEDEV_ETERNAL	created device will be never destroyed
 .Ed
 .Pp
 The
@@ -154,6 +155,18 @@ the device created is destroyed immediat
 drops his reference to cdev.
 .Pp
 The
+.Dv MAKEDEV_ETERNAL
+flag allows the kernel to not acquire some locks when translating system
+calls into the cdevsw methods calls.
+It is responsibility of the driver author to make sure that
+.Fn destroy_dev
+is never called on the returned cdev.
+For the convenience, use the
+.Dv MAKEDEV_ETERNAL_KLD
+flag for the code that can be compiled into kernel or loaded
+(and unloaded) as loadable module.
+.Pp
+The
 .Fn make_dev_cred
 function is equivalent to the call
 .Bd -literal -offset indent