[PATCH 1/4] driver: core: add subsys_driver() macro

[Brian Masney]

Add a new macro subsys_driver() to eliminate some boilerplate code in
drivers that need to register earlier in the boot at the subsys_initcall
level.

Signed-off-by: Brian Masney <bmasney@xxxxxxxxxx>
Assisted-by: Claude:claude-opus-4-8
---
 include/linux/device/driver.h | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

diff --git a/include/linux/device/driver.h b/include/linux/device/driver.h
index 768a1334c0a1..29fbc01ef06f 100644
--- a/include/linux/device/driver.h
+++ b/include/linux/device/driver.h
@@ -297,4 +297,35 @@ static int __init __driver##_init(void) \
 } \
 device_initcall(__driver##_init);
 
+/**
+ * subsys_driver() - Helper macro for drivers that don't do anything special
+ * in init/exit but have to register earlier, at subsys_initcall level, when
+ * built in. This eliminates a lot of boilerplate. Each driver may only use
+ * this macro once, and calling it replaces the init/exit boilerplate.
+ *
+ * @__driver: driver name
+ * @__register: register function for this driver type
+ * @__unregister: unregister function for this driver type
+ * @...: Additional arguments to be passed to __register and __unregister.
+ *
+ * This is meant to be a direct parallel of module_driver() above, but with
+ * the init call promoted to subsys_initcall() for built-in drivers so they
+ * are available earlier during boot. When built as a module subsys_initcall()
+ * collapses to module_init() and the normal module init/exit paths are used.
+ *
+ * Use this macro to construct bus specific macros for registering drivers,
+ * and do not use it on its own.
+ */
+#define subsys_driver(__driver, __register, __unregister, ...) \
+static int __init __driver##_init(void) \
+{ \
+	return __register(&(__driver), ##__VA_ARGS__); \
+} \
+subsys_initcall(__driver##_init) \
+static void __exit __driver##_exit(void) \
+{ \
+	__unregister(&(__driver), ##__VA_ARGS__); \
+} \
+module_exit(__driver##_exit)
+
 #endif	/* _DEVICE_DRIVER_H_ */

-- 
2.55.0