linux-kernel - Re: [GIT PULL] USB driver patches for 4.6-rc1

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Date:	Sun, 20 Mar 2016 19:31:47 +0800
From:	Peter Chen <hzpeterchen@...il.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Greg KH <gregkh@...uxfoundation.org>,
	Peter Chen <peter.chen@...escale.com>,
	Philipp Zabel <p.zabel@...gutronix.de>,
	Alan Stern <stern@...land.harvard.edu>,
	Rob Herring <robh@...nel.org>, Arnd Bergmann <arnd@...db.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	USB list <linux-usb@...r.kernel.org>
Subject: Re: [GIT PULL] USB driver patches for 4.6-rc1

On Fri, Mar 18, 2016 at 04:01:51PM -0700, Linus Torvalds wrote:
> On Fri, Mar 18, 2016 at 3:51 PM, Linus Torvalds
> <torvalds@...ux-foundation.org> wrote:
> >
> > The commit that ends up being marked bad is odd, but there it is:
> > 69bec7259853 "USB: core: let USB device know device node".
> 
> Confirmed. Not only did it bisect to that, reverting it on top of the
> current kernel fixes my machine.
> 
> So that commit is somehow buggy. I don't see what it does that would
> break even with OF disabled, but something does.
> 
> I'll just revert it. The way it is done seems bogus anyway.  It looks
> at of_node when OF is disabled, but generally that isn't even
> initialized as far as I can tell, and we have things like
> dev_of_node() helpers to make sure you don't do that.
> 

I am sorry to make things break, Nicolai Stange's found the root cause
for this problem, and his patch fixed it.

USB device structure (both struct usb_hcd and struct usb_device) is
initialized by kzalloc, so the struct device in it is initialized by
zero, and will not cause non-initialized for USB device, but you
are right, a good practice is using dev_of_node for all devices in
case the struct device is not zero-initialized.

-- 

Best Regards,
Peter Chen