linux-kernel - Re: [PATCH v4] usb: create usb_debug

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Date:   Tue, 4 Jun 2019 17:13:03 +0800
From:   Chunfeng Yun <chunfeng.yun@...iatek.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
CC:     Felipe Balbi <felipe.balbi@...ux.intel.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        <linux-usb@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-mediatek@...ts.infradead.org>
Subject: Re: [PATCH v4] usb: create usb_debug_root for gadget only

On Tue, 2019-06-04 at 10:24 +0200, Greg Kroah-Hartman wrote:
> On Tue, Jun 04, 2019 at 10:47:55AM +0300, Felipe Balbi wrote:
> > 
> > Hi,
> > 
> > Greg Kroah-Hartman <gregkh@...uxfoundation.org> writes:
> > >> +struct dentry *usb_debugfs_init(void)
> > >> +{
> > >> +	if (!usb_debug_root)
> > >> +		usb_debug_root = debugfs_create_dir("usb", NULL);
> > >> +
> > >> +	atomic_inc(&usb_debug_root_refcnt);
> > >> +
> > >> +	return usb_debug_root;
> > >> +}
> > >> +EXPORT_SYMBOL_GPL(usb_debugfs_init);
> > >> +
> > >> +void usb_debugfs_cleanup(void)
> > >> +{
> > >> +	if (atomic_dec_and_test(&usb_debug_root_refcnt)) {
> > >> +		debugfs_remove_recursive(usb_debug_root);
> > >> +		usb_debug_root = NULL;
> > >> +	}
> > >> +}
> > >> +EXPORT_SYMBOL_GPL(usb_debugfs_cleanup);
> > >
> > > Only remove the debugfs subdir if the usbcore module is removed.  Create
> > > the debugfs subdir when the usbcore module is loaded.  No need for any
> > > reference counting of any sort at all.  No need to overthink this :)
> > 
> > There is a slight need to overthink. He wants to use the same directory
> > for gadget-only builds too :-)
> 
> Again, that's fine, this file will be loaded for those builds as well,
> right?  
Yes, either usbcore or gadget will select this file.

> Otherwise, how would this code even be present?  :)
> 
> thanks,
> 
> greg k-h