[RFC PATCH] usb: common: change usb_debug_root as static variable

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

Try to avoid using extern global variable, and provide two
functions for the usage cases

Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
---
NOTE:
    Prepared but not send out patches for drivers using usb_debug_root,
because I'm not sure whether this patch is needed, and many drivers
will be modified.
---
 drivers/usb/common/common.c | 16 ++++++++++++++--
 include/linux/usb.h         |  5 ++++-
 2 files changed, 18 insertions(+), 3 deletions(-)

diff --git a/drivers/usb/common/common.c b/drivers/usb/common/common.c
index 1433260d99b4..639ee6d243a2 100644
--- a/drivers/usb/common/common.c
+++ b/drivers/usb/common/common.c
@@ -293,8 +293,20 @@ 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 struct dentry *usb_debug_root;
+
+struct dentry *usb_debugfs_create_dir(const char *name)
+{
+	return debugfs_create_dir(name, usb_debug_root);
+}
+EXPORT_SYMBOL_GPL(usb_debugfs_create_dir);
+
+struct dentry *usb_debugfs_create_file(const char *name, umode_t mode,
+			void *data, const struct file_operations *fops)
+{
+	return debugfs_create_file(name, mode, usb_debug_root, data, fops);
+}
+EXPORT_SYMBOL_GPL(usb_debugfs_create_file);
 
 static int __init usb_common_init(void)
 {
diff --git a/include/linux/usb.h b/include/linux/usb.h
index e656e7b4b1e4..ad96e0aa0127 100644
--- a/include/linux/usb.h
+++ b/include/linux/usb.h
@@ -2001,7 +2001,10 @@ extern void usb_register_notify(struct notifier_block *nb);
 extern void usb_unregister_notify(struct notifier_block *nb);
 
 /* debugfs stuff */
-extern struct dentry *usb_debug_root;
+extern struct dentry *usb_debugfs_create_dir(const char *name);
+extern struct dentry *
+usb_debugfs_create_file(const char *name, umode_t mode, void *data,
+			const struct file_operations *fops);
 
 /* LED triggers */
 enum usb_led_event {
-- 
2.23.0