drivers: base: handle module_kobject creation

module_add_driver() relies on module_kset list for
/sys/module/<built-in-module>/drivers directory creation.

Since,
commit 96a1a24 ("kernel/params.c: defer most of param_sysfs_init() to late_initcall time")
drivers which are initialized from subsys_initcall() or any other
higher precedence initcall couldn't find the related kobject entry
in the module_kset list because module_kset is not fully populated
by the time module_add_driver() refers it. As a consequence,
module_add_driver() returns early without calling make_driver_name().
Therefore, /sys/module/<built-in-module>/drivers is never created.

Fix this issue by letting module_add_driver() handle module_kobject
creation itself.

Fixes: 96a1a24 ("kernel/params.c: defer most of param_sysfs_init() to late_initcall time")
Cc: [email protected] # requires all other patches from the series
Suggested-by: Rasmus Villemoes <[email protected]>
Signed-off-by: Shyam Saini <[email protected]>
Acked-by: Greg Kroah-Hartman <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Petr Pavlu <[email protected]>

Author: Shyam Saini

drivers/base/module.c

@@ -42,16 +42,13 @@ int module_add_driver(struct module *mod, const struct device_driver *drv)
 	if (mod)
 		mk = &mod->mkobj;
 	else if (drv->mod_name) {
-		struct kobject *mkobj;
-
-		/* Lookup built-in module entry in /sys/modules */
-		mkobj = kset_find_obj(module_kset, drv->mod_name);
-		if (mkobj) {
-			mk = container_of(mkobj, struct module_kobject, kobj);
+		/* Lookup or create built-in module entry in /sys/modules */
+		mk = lookup_or_create_module_kobject(drv->mod_name);
+		if (mk) {
 			/* remember our module structure */
 			drv->p->mkobj = mk;
-			/* kset_find_obj took a reference */
-			kobject_put(mkobj);
+			/* lookup_or_create_module_kobject took a reference */
+			kobject_put(&mk->kobj);
 		}
 	}