USB: move usb debugfs directory creation to the usb common core

The USB gadget subsystem wants to use the USB debugfs root directory, so
move it to the common "core" USB code so that it is properly initialized
and removed as needed.

In order to properly do this, we need to load the common code before the
usb core code, when everything is linked into the kernel, so reorder the
link order of the code.

Also as the usb common code has the possibility of the led trigger logic
to be merged into it, handle the build option properly by only having
one module init/exit function and have the common code initialize the
led trigger if needed.

Reported-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
Cc: Felipe Balbi <felipe.balbi@linux.intel.com>
Tested-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/Makefile

@@ -5,6 +5,7 @@
 
 # Object files in subdirectories
 
+obj-$(CONFIG_USB_COMMON)	+= common/
 obj-$(CONFIG_USB)		+= core/
 obj-$(CONFIG_USB_SUPPORT)	+= phy/
 
@@ -60,8 +61,6 @@ obj-$(CONFIG_USB_CHIPIDEA)	+= chipidea/
 obj-$(CONFIG_USB_RENESAS_USBHS)	+= renesas_usbhs/
 obj-$(CONFIG_USB_GADGET)	+= gadget/
 
-obj-$(CONFIG_USB_COMMON)	+= common/
-
 obj-$(CONFIG_USBIP_CORE)	+= usbip/
 
 obj-$(CONFIG_TYPEC)		+= typec/

drivers/usb/common/common.c

@@ -15,6 +15,8 @@
 #include <linux/usb/of.h>
 #include <linux/usb/otg.h>
 #include <linux/of_platform.h>
+#include <linux/debugfs.h>
+#include "common.h"
 
 static const char *const ep_type_names[] = {
 	[USB_ENDPOINT_XFER_CONTROL] = "ctrl",
@@ -291,4 +293,23 @@ struct device *usb_of_get_companion_dev(struct device *dev)
 EXPORT_SYMBOL_GPL(usb_of_get_companion_dev);
 #endif
 
+struct dentry *usb_debug_root;
+EXPORT_SYMBOL_GPL(usb_debug_root);
+
+static int __init usb_common_init(void)
+{
+	usb_debug_root = debugfs_create_dir("usb", NULL);
+	ledtrig_usb_init();
+	return 0;
+}
+
+static void __exit usb_common_exit(void)
+{
+	ledtrig_usb_exit();
+	debugfs_remove_recursive(usb_debug_root);
+}
+
+subsys_initcall(usb_common_init);
+module_exit(usb_common_exit);
+
 MODULE_LICENSE("GPL");

drivers/usb/common/common.h

@@ -0,0 +1,14 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef __LINUX_USB_COMMON_H
+#define __LINUX_USB_COMMON_H
+
+#if defined(CONFIG_USB_LED_TRIG)
+void ledtrig_usb_init(void);
+void ledtrig_usb_exit(void);
+#else
+static inline void ledtrig_usb_init(void) { }
+static inline void ledtrig_usb_exit(void) { }
+#endif
+
+#endif	/* __LINUX_USB_COMMON_H */

drivers/usb/common/led.c

@@ -10,6 +10,7 @@
 #include <linux/init.h>
 #include <linux/leds.h>
 #include <linux/usb.h>
+#include "common.h"
 
 #define BLINK_DELAY 30
 
@@ -36,18 +37,14 @@ void usb_led_activity(enum usb_led_event ev)
 EXPORT_SYMBOL_GPL(usb_led_activity);
 
 
-static int __init ledtrig_usb_init(void)
+void __init ledtrig_usb_init(void)
 {
 	led_trigger_register_simple("usb-gadget", &ledtrig_usb_gadget);
 	led_trigger_register_simple("usb-host", &ledtrig_usb_host);
-	return 0;
 }
 
-static void __exit ledtrig_usb_exit(void)
+void __exit ledtrig_usb_exit(void)
 {
 	led_trigger_unregister_simple(ledtrig_usb_gadget);
 	led_trigger_unregister_simple(ledtrig_usb_host);
 }
-
-module_init(ledtrig_usb_init);
-module_exit(ledtrig_usb_exit);

drivers/usb/core/usb.c

@@ -1185,19 +1185,17 @@ static struct notifier_block usb_bus_nb = {
 	.notifier_call = usb_bus_notify,
 };
 
-struct dentry *usb_debug_root;
-EXPORT_SYMBOL_GPL(usb_debug_root);
+static struct dentry *usb_devices_root;
 
 static void usb_debugfs_init(void)
 {
-	usb_debug_root = debugfs_create_dir("usb", NULL);
-	debugfs_create_file("devices", 0444, usb_debug_root, NULL,
-			    &usbfs_devices_fops);
+	usb_devices_root = debugfs_create_file("devices", 0444, usb_debug_root,
+					       NULL, &usbfs_devices_fops);
 }
 
 static void usb_debugfs_cleanup(void)
 {
-	debugfs_remove_recursive(usb_debug_root);
+	debugfs_remove(usb_devices_root);
 }
 
 /*