[PATCH v4 3/9] mm/memory_hotplug: export mhp_get_default_online_type

[Gregory Price]

Drivers which may pass hotplug policy down to DAX need MMOP_ symbols
and the mhp_get_default_online_type function for hotplug use cases.

Some drivers (cxl) co-mingle their hotplug and devdax use-cases into
the same driver code, and chose the dax_kmem path as the default driver
path - making it difficult to require hotplug as a predicate to building
the overall driver (it may break other non-hotplug use-cases).

Export mhp_get_default_online_type function to allow these drivers to
build when hotplug is disabled and still use the DAX use case.

In the built-out case we simply return MMOP_OFFLINE as it's
non-destructive.  The internal function can never return -1 either,
so we choose this to allow for defining the function with 'enum mmop'.

Signed-off-by: Gregory Price <gourry@xxxxxxxxxx>
---
 include/linux/memory_hotplug.h | 2 ++
 mm/memory_hotplug.c            | 1 +
 2 files changed, 3 insertions(+)

diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
index 7c9d66729c60..f059025f8f8b 100644
--- a/include/linux/memory_hotplug.h
+++ b/include/linux/memory_hotplug.h
@@ -316,6 +316,8 @@ extern struct zone *zone_for_pfn_range(enum mmop online_type,
 extern int arch_create_linear_mapping(int nid, u64 start, u64 size,
 				      struct mhp_params *params);
 void arch_remove_linear_mapping(u64 start, u64 size);
+#else
+static inline enum mmop mhp_get_default_online_type(void) { return MMOP_OFFLINE; }
 #endif /* CONFIG_MEMORY_HOTPLUG */
 
 #endif /* __LINUX_MEMORY_HOTPLUG_H */
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 6833208cc17c..494257054095 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -239,6 +239,7 @@ enum mmop mhp_get_default_online_type(void)
 
 	return mhp_default_online_type;
 }
+EXPORT_SYMBOL_GPL(mhp_get_default_online_type);
 
 void mhp_set_default_online_type(enum mmop online_type)
 {
-- 
2.54.0