From bc6a0cbd576c66995d782331456f68ae63a50af4 Mon Sep 17 00:00:00 2001
From: Pavel Machek <pavel@ucw.cz>
Date: Fri, 23 Apr 2010 20:32:29 +0200
Subject: PM / Hibernate: document open(/dev/snapshot) side effects

Opening and closing /dev/snapshot causes the kernel to carry out
some hibernate preparations that should be documented.

[rjw: Added the changelog.]

Signed-off-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
---
 Documentation/power/userland-swsusp.txt | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/Documentation/power/userland-swsusp.txt b/Documentation/power/userland-swsusp.txt
index b967cd9137d6..81680f9f5909 100644
--- a/Documentation/power/userland-swsusp.txt
+++ b/Documentation/power/userland-swsusp.txt
@@ -24,6 +24,10 @@ assumed to be in the resume mode.  The device cannot be open for simultaneous
 reading and writing.  It is also impossible to have the device open more than
 once at a time.
 
+Even opening the device has side effects. Data structures are
+allocated, and PM_HIBERNATION_PREPARE / PM_RESTORE_PREPARE chains are
+called.
+
 The ioctl() commands recognized by the device are:
 
 SNAPSHOT_FREEZE - freeze user space processes (the current process is
-- 
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