kernel: ksysfs: initialize kernel_kobj earlier

Software nodes depend on kernel_kobj which is initialized pretty late
into the boot process - as a core_initcall(). Ahead of moving the
software node initialization to driver_init() we must first make
kernel_kobj available before it.

Make ksysfs_init() visible in a new header - ksysfs.h - and call it in
do_basic_setup() right before driver_init().

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>
Link: https://patch.msgid.link/20260402-nokia770-gpio-swnodes-v5-1-d730db3dd299@oss.qualcomm.com
Signed-off-by: Danilo Krummrich <dakr@kernel.org>

Author: Bartosz Golaszewski

MAINTAINERS

@@ -7805,6 +7805,7 @@ F:	include/linux/debugfs.h
 F:	include/linux/device.h
 F:	include/linux/fwnode.h
 F:	include/linux/kobj*
+F:	include/linux/ksysfs.h
 F:	include/linux/property.h
 F:	include/linux/sysfs.h
 F:	kernel/ksysfs.c

include/linux/ksysfs.h

@@ -0,0 +1,8 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef _KSYSFS_H_
+#define _KSYSFS_H_
+
+void ksysfs_init(void);
+
+#endif /* _KSYSFS_H_ */

init/main.c

@@ -36,6 +36,7 @@
 #include <linux/kmod.h>
 #include <linux/kprobes.h>
 #include <linux/kmsan.h>
+#include <linux/ksysfs.h>
 #include <linux/vmalloc.h>
 #include <linux/kernel_stat.h>
 #include <linux/start_kernel.h>
@@ -1473,6 +1474,7 @@ static void __init do_initcalls(void)
 static void __init do_basic_setup(void)
 {
 	cpuset_init_smp();
+	ksysfs_init();
 	driver_init();
 	init_irq_proc();
 	do_ctors();

kernel/ksysfs.c

@@ -8,6 +8,7 @@
 
 #include <asm/byteorder.h>
 #include <linux/kobject.h>
+#include <linux/ksysfs.h>
 #include <linux/string.h>
 #include <linux/sysfs.h>
 #include <linux/export.h>
@@ -213,7 +214,7 @@ static const struct attribute_group kernel_attr_group = {
 	.attrs = kernel_attrs,
 };
 
-static int __init ksysfs_init(void)
+void __init ksysfs_init(void)
 {
 	int error;
 
@@ -234,14 +235,12 @@ static int __init ksysfs_init(void)
 			goto group_exit;
 	}
 
-	return 0;
+	return;
 
 group_exit:
 	sysfs_remove_group(kernel_kobj, &kernel_attr_group);
 kset_exit:
 	kobject_put(kernel_kobj);
 exit:
-	return error;
+	pr_err("failed to initialize the kernel kobject: %d\n", error);
 }
-
-core_initcall(ksysfs_init);