document the "security" command

sbin/atactl/atactl.8

@@ -1,4 +1,4 @@
-.\"	$NetBSD: atactl.8,v 1.19 2004/10/10 09:45:10 wiz Exp $
+.\"	$NetBSD: atactl.8,v 1.20 2005/04/12 11:41:14 drochner Exp $
 .\"
 .\" Copyright (c) 1998 The NetBSD Foundation, Inc.
 .\" All rights reserved.
@@ -34,7 +34,7 @@
 .\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 .\" POSSIBILITY OF SUCH DAMAGE.
 .\"
-.Dd October 10, 2004
+.Dd April 12, 2005
 .Dt ATACTL 8
 .Os
 .Sh NAME
@@ -174,6 +174,31 @@ Prints the error log.
 .Ar selftest-log
 .Pp
 Prints the self-test log.
+.Pp
+.Cm security
+.Ar [freeze | status]
+.Pp
+Controls
+.Dq security
+(password protection) features of modern ATA drives.
+The security commands are intended to be issued by low-level
+software (firmware / BIOS) only.
+Generally, the security status should be
+.Dq frozen
+before the operating system is started so that misbehaving or malicious
+software cannot set or change a password.
+Older and buggy BIOSes neglect to do so; in these cases it might make
+sense to issue the
+.Dq freeze
+command early in the boot process.
+.Pp
+.Ar freeze
+.Pp
+freezes the drive's security status
+.Pp
+.Ar status
+.Pp
+displays the drive's security status
 .Sh BUS COMMANDS
 The following commands may be used on IDE and ATA busses.
 Note that not all devices support all commands.