[v3 PATCH] usb: create usb_debug_root for gadget only

[Chunfeng Yun <chunfeng.yun@mediatek.com>]

When CONFIG_USB is not set, and CONFIG_USB_GADGET is set,
there is an issue, e.g.:

drivers/usb/mtu3/mtu3_debugfs.o: in function 'ssusb_debugfs_create_root':
mtu3_debugfs.c:(.text+0xba3): undefined reference to 'usb_debug_root'

usb_debug_root is currently only built when host is supported
(CONFIG_USB is set), for convenience, we also want it created when
gadget only is enabled, this patch try to support it.

Reported-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
---
v3:
  1. still create usb_debug_root for gadget only
  2. abandon mtu3's change
  3. drop acked-by Randy

v2(resend): add acked-by Randy

v1: fix mtu3's build error, replace usb_debug_root by NULL;
---
 drivers/usb/core/usb.c        |  2 +-
 drivers/usb/gadget/udc/core.c | 27 +++++++++++++++++++++++++++
 include/linux/usb.h           |  1 +
 3 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/core/usb.c b/drivers/usb/core/usb.c
index 7fcb9f782931..88b3ee03a12d 100644
--- a/drivers/usb/core/usb.c
+++ b/drivers/usb/core/usb.c
@@ -1190,7 +1190,7 @@ EXPORT_SYMBOL_GPL(usb_debug_root);
 
 static void usb_debugfs_init(void)
 {
-	usb_debug_root = debugfs_create_dir("usb", NULL);
+	usb_debug_root = debugfs_create_dir(USB_DEBUG_ROOT_NAME, NULL);
 	debugfs_create_file("devices", 0444, usb_debug_root, NULL,
 			    &usbfs_devices_fops);
 }
diff --git a/drivers/usb/gadget/udc/core.c b/drivers/usb/gadget/udc/core.c
index 7cf34beb50df..ed45f9429e58 100644
--- a/drivers/usb/gadget/udc/core.c
+++ b/drivers/usb/gadget/udc/core.c
@@ -8,6 +8,7 @@
 
 #include <linux/kernel.h>
 #include <linux/module.h>
+#include <linux/debugfs.h>
 #include <linux/device.h>
 #include <linux/list.h>
 #include <linux/err.h>
@@ -1587,12 +1588,37 @@ static int usb_udc_uevent(struct device *dev, struct kobj_uevent_env *env)
 	return 0;
 }
 
+/* if CONFIG_USB is set, leave USB core to create usb_debug_root */
+#ifndef CONFIG_USB
+struct dentry *usb_debug_root;
+EXPORT_SYMBOL_GPL(usb_debug_root);
+
+static void usb_debugfs_init(void)
+{
+	usb_debug_root = debugfs_create_dir(USB_DEBUG_ROOT_NAME, NULL);
+}
+
+static void usb_debugfs_cleanup(void)
+{
+	debugfs_remove_recursive(usb_debug_root);
+}
+#else
+static void usb_debugfs_init(void)
+{}
+
+static void usb_debugfs_cleanup(void)
+{}
+#endif
+
 static int __init usb_udc_init(void)
 {
+	usb_debugfs_init();
+
 	udc_class = class_create(THIS_MODULE, "udc");
 	if (IS_ERR(udc_class)) {
 		pr_err("failed to create udc class --> %ld\n",
 				PTR_ERR(udc_class));
+		usb_debugfs_cleanup();
 		return PTR_ERR(udc_class);
 	}
 
@@ -1604,6 +1630,7 @@ subsys_initcall(usb_udc_init);
 static void __exit usb_udc_exit(void)
 {
 	class_destroy(udc_class);
+	usb_debugfs_cleanup();
 }
 module_exit(usb_udc_exit);
 
diff --git a/include/linux/usb.h b/include/linux/usb.h
index ae82d9d1112b..9c6e7b3265af 100644
--- a/include/linux/usb.h
+++ b/include/linux/usb.h
@@ -1994,6 +1994,7 @@ extern void usb_register_notify(struct notifier_block *nb);
 extern void usb_unregister_notify(struct notifier_block *nb);
 
 /* debugfs stuff */
+#define USB_DEBUG_ROOT_NAME	"usb"
 extern struct dentry *usb_debug_root;
 
 /* LED triggers */
-- 
2.21.0