lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  PHC 
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:	Mon, 22 Dec 2014 16:04:53 -0500 (EST)
From:	Alan Stern <>
To:	Doug Anderson <>
cc:	Wu Liang feng <>,
	Heiko Stübner <>,
	Tao Huang <>,
	Kever Yang <>,
	Eddie Cai <>,
	Roy Li <>, Chris <>,
	Julius Werner <>,
	Pawel Osciak <>,
	Tomasz Figa <>,
	"" <>,
	"" <>
Subject: Re: [PATCH 2/2] USB: ehci-platform: Support ehci reset after resume

On Mon, 22 Dec 2014, Doug Anderson wrote:

> Alan,
> On Mon, Dec 22, 2014 at 8:06 AM, Alan Stern <> wrote:
> > On Mon, 22 Dec 2014, Wu Liang feng wrote:
> >
> >> The EHCI controller doesn't properly detect the case when
> >
> > "The" EHCI controller?  I don't know what EHCI controller you're
> > talking about, but my controllers don't have any trouble detecting
> > device removal during suspend.
> This is specifically the EHCI controller on rk3288.  Not sure why Wu
> Liang feng removed that part of the description.

Maybe it could be put back in.

> > Isn't this solution too extreme?  What if the device was a flash
> > storage drive and it wasn't unplugged during suspend?  This patch would
> > force it to be removed, messing up any mounted filesystems, when there
> > was no need.
> I'm told by Julius (CCed, who knows the USB stack infinitely better
> than I do) that you can work around this using "persist".  I would
> imagine that anyone on a machine using hibernation would run into the
> same problem, right?

> We asked a lot about this and you can find a whole set of detailed
> discussion at:
> Since I don't know the USB subsystem particularly well, my review
> isn't terribly meaningful, but just in case:
> Reviewed-by: Doug Anderson <>
> On rk3288-pinky I have tested that without this patch the EHCI
> controller flips out when a USB webcam is plugged into the port and is
> power cycled across suspend/resume.  With this patch the controller
> properly unplugs / replugs the webcam.
> Tested-by: Doug Anderson <>

I assume you also tested the case where the webcam is _not_ 
power-cycled during the suspend.

On Mon, 22 Dec 2014, Julius Werner wrote:

> As Doug said, I think persist is the solution. We have essentially the
> same case: all we know is that there is now a device connected to the 
> same port that a device had been connected during suspend... but with 
> no guarantees whether it is the same device or in the same state. By  
> forcing people to use persist, we acknowledge that this has the same  
> risks (e.g. data corruption if a mounted mass storage device was
> swapped out for another one), and we benefit from the same safety
> checks like comparing the serial number.

Okay, I see.  This makes sense.

Acked-by: Alan Stern <>

Alan Stern

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to
More majordomo info at
Please read the FAQ at

Powered by blists - more mailing lists