[PATCH v4 2/4] PM: hibernate: add pm_hibernation_snapshot_done() helper

Some subsystem resume callbacks do not receive the PM event and
therefore cannot distinguish the PMSG_THAW phase after snapshot creation
from the PMSG_RESTORE phase.

Export pm_hibernation_snapshot_done() so a driver can query whether the
hibernation snapshot has been created and is still available.  The helper
only exposes the PM state; callers remain responsible for ensuring that
any device-specific behavior is safe, including subsequent poweroff or
shutdown handling.

The helper returns !!in_suspend.  This variable is set before
swsusp_arch_suspend(), cleared before the snapshot memory is released,
and marked __nosavedata, so it remains clear on the restore path.

Acked-by: Rafael J. Wysocki (Intel) <[email protected]>
Signed-off-by: Haowen Tu <[email protected]>
---
 include/linux/suspend.h  |  2 ++
 kernel/power/hibernate.c | 12 ++++++++++++
 2 files changed, 14 insertions(+)

diff --git a/include/linux/suspend.h b/include/linux/suspend.h
index b02876f1ae38..2cebbec3e2f7 100644
--- a/include/linux/suspend.h
+++ b/include/linux/suspend.h
@@ -393,6 +393,7 @@ extern void hibernation_set_ops(const struct platform_hibernation_ops *ops);
 extern int hibernate(void);
 extern bool system_entering_hibernation(void);
 extern bool hibernation_available(void);
+bool pm_hibernation_snapshot_done(void);
 asmlinkage int swsusp_save(void);
 extern struct pbe *restore_pblist;
 int pfn_is_nosave(unsigned long pfn);
@@ -412,6 +413,7 @@ static inline void hibernation_set_ops(const struct platform_hibernation_ops *op
 static inline int hibernate(void) { return -ENOSYS; }
 static inline bool system_entering_hibernation(void) { return false; }
 static inline bool hibernation_available(void) { return false; }
+static inline bool pm_hibernation_snapshot_done(void) { return false; }
 
 static inline int hibernate_quiet_exec(int (*func)(void *data), void *data) {
 	return -ENOTSUPP;
diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
index 6d3e637c5a02..045d29f55011 100644
--- a/kernel/power/hibernate.c
+++ b/kernel/power/hibernate.c
@@ -113,6 +113,18 @@ bool hibernation_available(void)
 		!secretmem_active() && !cxl_mem_active();
 }
 
+/**
+ * pm_hibernation_snapshot_done - check if a hibernation snapshot is available
+ *
+ * Return: %true if a hibernation snapshot has been taken and has not been
+ *         released yet.
+ */
+bool pm_hibernation_snapshot_done(void)
+{
+	return !!in_suspend;
+}
+EXPORT_SYMBOL_GPL(pm_hibernation_snapshot_done);
+
 /**
  * hibernation_set_ops - Set the global hibernate operations.
  * @ops: Hibernation operations to use in subsequent hibernation transitions.
-- 
2.20.1