dm: add helper macro for simple DM target module init and exit

Eliminate duplicate boilerplate code for simple modules that contain
a single DM target driver without any additional setup code.

Add a new module_dm() macro, which replaces the module_init() and
module_exit() with template functions that call dm_register_target()
and dm_unregister_target() respectively.

Signed-off-by: Yangtao Li <frank.li@vivo.com>
Signed-off-by: Mike Snitzer <snitzer@kernel.org>

1 files changed, 20 insertions, 0 deletions

diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h
index 8aa6b3ea91fa..f2d9afb8a7e9 100644
--- a/include/linux/device-mapper.h
+++ b/include/linux/device-mapper.h
@@ -631,6 +631,26 @@ void dm_destroy_crypto_profile(struct blk_crypto_profile *profile);
 		DMEMIT("target_name=%s,target_version=%u.%u.%u", \
 		       (y)->name, (y)->version[0], (y)->version[1], (y)->version[2])
 
+/**
+ * module_dm() - Helper macro for DM targets that don't do anything
+ * special in their module_init and module_exit.
+ * Each module may only use this macro once, and calling it replaces
+ * module_init() and module_exit().
+ *
+ * @name: DM target's name
+ */
+#define module_dm(name) \
+static int __init dm_##name##_init(void) \
+{ \
+	return dm_register_target(&(name##_target)); \
+} \
+module_init(dm_##name##_init) \
+static void __exit dm_##name##_exit(void) \
+{ \
+	dm_unregister_target(&(name##_target)); \
+} \
+module_exit(dm_##name##_exit)
+
 /*
  * Definitions of return values from target end_io function.
  */