[PATCH v3] USB: gadget: Add ID numbers to configfs-gadget driver names

[Chanh Nguyen <chanh@os.amperecomputing.com>]

It is unable to use configfs to attach more than one gadget. When
attaching the second gadget, it always fails and the kernel message
prints out:

Error: Driver 'configfs-gadget' is already registered, aborting...
UDC core: g1: driver registration failed: -16

This commit fixes the problem by using the gadget name as a suffix
to each configfs_gadget's driver name, thus making the names
distinct.

Fixes: fc274c1e9973 ("USB: gadget: Add a new bus for gadgets")
Signed-off-by: Chanh Nguyen <chanh@os.amperecomputing.com>

---
Changes in v3:
  - Use the gadget name as a unique suffix instead     [Andrzej]
  - Remove the driver.name allocation by template        [Chanh]
  - Update commit message                                [Chanh]

Changes in v2:
  - Replace scnprintf() by kasprintf() to simplify the code [CJ]
  - Move the clean up code from gadgets_drop() to
    gadget_info_attr_release()                        [Frank Li]
  - Correct the resource free up in gadges_make()   [Alan Stern]
  - Remove the unnecessary variable in gadgets_make()    [Chanh]
  - Fixes minor grammar issue in commit message          [Chanh]
---
 drivers/usb/gadget/configfs.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/gadget/configfs.c b/drivers/usb/gadget/configfs.c
index 96121d1c8df4..0853536cbf2e 100644
--- a/drivers/usb/gadget/configfs.c
+++ b/drivers/usb/gadget/configfs.c
@@ -393,6 +393,7 @@ static void gadget_info_attr_release(struct config_item *item)
 	WARN_ON(!list_empty(&gi->string_list));
 	WARN_ON(!list_empty(&gi->available_func));
 	kfree(gi->composite.gadget_driver.function);
+	kfree(gi->composite.gadget_driver.driver.name);
 	kfree(gi);
 }
 
@@ -1572,7 +1573,6 @@ static const struct usb_gadget_driver configfs_driver_template = {
 	.max_speed	= USB_SPEED_SUPER_PLUS,
 	.driver = {
 		.owner          = THIS_MODULE,
-		.name		= "configfs-gadget",
 	},
 	.match_existing_only = 1,
 };
@@ -1623,13 +1623,21 @@ static struct config_group *gadgets_make(
 
 	gi->composite.gadget_driver = configfs_driver_template;
 
+	gi->composite.gadget_driver.driver.name = kasprintf(GFP_KERNEL,
+							    "configfs-gadget.%s", name);
+	if (!gi->composite.gadget_driver.driver.name)
+		goto err;
+
 	gi->composite.gadget_driver.function = kstrdup(name, GFP_KERNEL);
 	gi->composite.name = gi->composite.gadget_driver.function;
 
 	if (!gi->composite.gadget_driver.function)
-		goto err;
+		goto out_free_driver_name;
 
 	return &gi->group;
+
+out_free_driver_name:
+	kfree(gi->composite.gadget_driver.driver.name);
 err:
 	kfree(gi);
 	return ERR_PTR(-ENOMEM);
-- 
2.17.1