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

[Andrzej Pietrasiewicz <andrzej.p@collabora.com>]

Hello,

W dniu 11.01.2023 o 07:51, Chanh Nguyen pisze:
> 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);

This line is 88 chars long, which means you're taking advantage of checkpatch
allowing 100 columns nowadays. That's absolutely fine. If you collapse the above
two lines into one, the combined length is exactly 100 chars, so you might
just as well use a single line. In any case (collapsed or not) you can add my

Reviewed-by: Andrzej Pietrasiewicz <andrzej.p@collabora.com>

> +	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);