[PATCH v3 4/5] PM: Add visible HIBERNATION_INTERFACE and hide HIBERNATION

[Shriram Rajagopalan <rshriram@cs.ubc.ca>]

HIBERNATION covers the main hibernation control code and freeze-thaw
pm events, that xen's save/restore also uses. Explicitly enabling
an independant hibernation functionality to enable xen's save/restore
is a bit ugly. Define a new user visible symbol HIBERNATION_INTERFACE
that "selects" HIBERNATION and covers the main hibernation control code
instead of HIBERNATION. This way, we can also make XEN_SAVE_RESTORE
"select" HIBERNATION, enabling only the freeze-thaw code.

Signed-off-by: Shriram Rajagopalan <rshriram@cs.ubc.ca>
---
 kernel/power/Kconfig     |    9 +++++++--
 kernel/power/hibernate.c |    4 ++++
 kernel/power/main.c      |    2 +-
 kernel/power/user.c      |    2 ++
 4 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/kernel/power/Kconfig b/kernel/power/Kconfig
index 4603f08..493c678 100644
--- a/kernel/power/Kconfig
+++ b/kernel/power/Kconfig
@@ -19,10 +19,15 @@ config SUSPEND_FREEZER
 	  Turning OFF this setting is NOT recommended! If in doubt, say Y.
 
 config HIBERNATION
-	bool "Hibernation (aka 'suspend to disk')"
-	depends on SWAP && ARCH_HIBERNATION_POSSIBLE
+	def_bool n
+	depends on ARCH_HIBERNATION_POSSIBLE
 	select LZO_COMPRESS
 	select LZO_DECOMPRESS
+
+config HIBERNATION_INTERFACE
+	bool "Hibernation (aka 'suspend to disk')"
+	depends on SWAP
+	select HIBERNATION
 	---help---
 	  Enable the suspend to disk (STD) functionality, which is usually
 	  called "hibernation" in user interfaces.  STD checkpoints the
diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
index 1832bd2..13bcf69 100644
--- a/kernel/power/hibernate.c
+++ b/kernel/power/hibernate.c
@@ -592,6 +592,7 @@ static int prepare_processes(void)
  *	hibernate - The granpappy of the built-in hibernation management
  */
 
+#ifdef CONFIG_HIBERNATION_INTERFACE
 int hibernate(void)
 {
 	int error;
@@ -667,6 +668,8 @@ int hibernate(void)
 	return error;
 }
 
+#else /* !CONFIG_HIBERNATION_INTERFACE */
+int hibernate(void) { return -ENOSYS; }
 
 /**
  *	software_resume - Resume from a saved image.
@@ -1029,3 +1032,4 @@ __setup("noresume", noresume_setup);
 __setup("resume_offset=", resume_offset_setup);
 __setup("resume=", resume_setup);
 __setup("hibernate=", hibernate_setup);
+#endif /* !CONFIG_HIBERNATION_INTERFACE */
diff --git a/kernel/power/main.c b/kernel/power/main.c
index 8eaba5f..686a130 100644
--- a/kernel/power/main.c
+++ b/kernel/power/main.c
@@ -156,7 +156,7 @@ static ssize_t state_show(struct kobject *kobj, struct kobj_attribute *attr,
 			s += sprintf(s,"%s ", pm_states[i]);
 	}
 #endif
-#ifdef CONFIG_HIBERNATION
+#ifdef CONFIG_HIBERNATION_INTERFACE
 	s += sprintf(s, "%s\n", "disk");
 #else
 	if (s != buf)
diff --git a/kernel/power/user.c b/kernel/power/user.c
index c36c3b9..5f36ee7 100644
--- a/kernel/power/user.c
+++ b/kernel/power/user.c
@@ -458,6 +458,7 @@ static long snapshot_ioctl(struct file *filp, unsigned int cmd,
 	return error;
 }
 
+#ifdef CONFIG_HIBERNATION_INTERFACE
 static const struct file_operations snapshot_fops = {
 	.open = snapshot_open,
 	.release = snapshot_release,
@@ -479,3 +480,4 @@ static int __init snapshot_device_init(void)
 };
 
 device_initcall(snapshot_device_init);
+#endif /* CONFIG_HIBERNATION_INTERFACE */
-- 
1.7.0.4