linux-kernel - Re: [PATCH v3 1/2] usb: dwc3: make dwc3_debugfs

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Date:	Mon, 11 Apr 2016 11:14:26 +0300
From:	Felipe Balbi <balbi@...nel.org>
To:	changbin.du@...el.com
Cc:	gregkh@...uxfoundation.org, linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	"Du\, Changbin" <changbin.du@...el.com>
Subject: Re: [PATCH v3 1/2] usb: dwc3: make dwc3_debugfs_init return value be void


Hi,

changbin.du@...el.com writes:
> diff --git a/drivers/usb/dwc3/debug.h b/drivers/usb/dwc3/debug.h
> index 07fbc2d..71e3180 100644
> --- a/drivers/usb/dwc3/debug.h
> +++ b/drivers/usb/dwc3/debug.h
> @@ -217,11 +217,11 @@ static inline const char *dwc3_gadget_event_type_string(u8 event)
>  void dwc3_trace(void (*trace)(struct va_format *), const char *fmt, ...);
>  
>  #ifdef CONFIG_DEBUG_FS
> -extern int dwc3_debugfs_init(struct dwc3 *);
> +extern void dwc3_debugfs_init(struct dwc3 *);
>  extern void dwc3_debugfs_exit(struct dwc3 *);
>  #else
> -static inline int dwc3_debugfs_init(struct dwc3 *d)
> -{  return 0;  }
> +static inline void dwc3_debugfs_init(struct dwc3 *d)
> +{  }
>  static inline void dwc3_debugfs_exit(struct dwc3 *d)
>  {  }
>  #endif
> diff --git a/drivers/usb/dwc3/debugfs.c b/drivers/usb/dwc3/debugfs.c
> index 9ac37fe..071b286 100644
> --- a/drivers/usb/dwc3/debugfs.c
> +++ b/drivers/usb/dwc3/debugfs.c
> @@ -618,69 +618,39 @@ static const struct file_operations dwc3_link_state_fops = {
>  	.release		= single_release,
>  };
>  
> -int dwc3_debugfs_init(struct dwc3 *dwc)
> +void dwc3_debugfs_init(struct dwc3 *dwc)
>  {
>  	struct dentry		*root;
> -	struct dentry		*file;
> -	int			ret;
>  
>  	root = debugfs_create_dir(dev_name(dwc->dev), NULL);
> -	if (!root) {
> -		ret = -ENOMEM;
> -		goto err0;
> -	}
> +	if (IS_ERR_OR_NULL(root))
> +		return;

We can definitely keep on going, but I'd still like to know that we
enabled CONFIG_DEBUG_FS but failed to create a file or a
directory. Seems like this should read as follows:

	if (IS_ERR_OR_NULL(root)) {
        	if (!root)
                	dev_err(dwc->dev, "Can't create debugfs root\n");
        	return;
	}

ditto to all bellow.

>  	dwc->root = root;
>  
>  	dwc->regset = kzalloc(sizeof(*dwc->regset), GFP_KERNEL);
>  	if (!dwc->regset) {
> -		ret = -ENOMEM;
> -		goto err1;
> +		debugfs_remove_recursive(root);

you're now duplicating debugfs_remove_recursive(root) in all braches and
that's error prone. It's probably better to keep our gotos, but change
them so they read as follows:

	if (!dwc->regset)
        	goto err1;

	[...]

        return; /* this is our successful exit point */

err1:
	debugfs_remove_recursive(root);
        kfree(dwc->regset);


-- 
balbi

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