Date: Thu, 15 Jan 2009 16:19:49 -0500 (EST)
From: Alan Stern <stern@rowland.harvard.edu>
To: Stefan Lippers-Hollmann <s.L-H@gmx.de>
cc: Greg KH <gregkh@suse.de>, <linux-kernel@vger.kernel.org>,
       <stable@kernel.org>, <linux-usb@vger.kernel.org>
Subject: Re: [patch 00/94] 2.6.28.1 stable review
In-Reply-To: <200901152200.04272.s.L-H@gmx.de>
Message-ID: <Pine.LNX.4.44L0.0901151617300.2181-100000@iolanthe.rowland.org>
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On Thu, 15 Jan 2009, Stefan Lippers-Hollmann wrote:

> Please consider adding the following patch, referring to
> http://bugzilla.kernel.org/show_bug.cgi?id=12301
> 
> commit 2caf7fcdb8532045680f06b67b9e63f0c9613aaa
> Author: Alan Stern <stern@rowland.harvard.edu>
> Date:   Wed Dec 31 11:31:33 2008 -0500
> 
>     USB: re-enable interface after driver unbinds
> 
>     This patch (as1197) fixes an error introduced recently.  Since a
>     significant number of devices can't handle Set-Interface requests, we
>     no longer call usb_set_interface() when a driver unbinds from an
>     interface, provided the interface is already in altsetting 0.  However
>     the interface still does get disabled, and the call to
>     usb_set_interface() was the only thing re-enabling it.  Since the
>     interface doesn't get re-enabled, further attempts to use it fail.
> 
>     So the patch adds a call to usb_enable_interface() when a driver
>     unbinds and the interface is in altsetting 0.  For this to work
>     right, the interface's endpoints have to be re-enabled but their
>     toggles have to be left alone.  Therefore an additional argument is
>     added to usb_enable_endpoint() and usb_enable_interface(), a flag
>     indicating whether or not the endpoint toggles should be reset.
> 
>     This is a forward-ported version of a patch which fixes Bugzilla
>     #12301.
> 
>     Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
>     Reported-by: David Roka <roka@dawid.hu>
>     Reported-by: Erik Ekman <erik@kryo.se>
>     Tested-by: Erik Ekman <erik@kryo.se>
>     Tested-by: Alon Bar-Lev <alon.barlev@gmail.com>
>     Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
> 
> This patch seems to fix other USB related issues in 2.6.28 as well, for 
> example:
> - random failures to boot from usb-storage (sometimes it works, sometimes 
>   it's slower to detect the rootfs, sometimes it fails alltogether)
> - problems to detect USB scanners (Epson snapscan (3490), invoking xsane 
>   the first time fails to detect the scanner, the second time the scanner 
>   warms up, but fails to get detected by xsane, the third time it finally 
>   works - sometimes it works directly).
> - issues to connect a ZyDAS zd1211rw based USB wlan stick through wpa2psk 
>   with wpasupplicant.
> 
> Adding this patch (slightly backported to 2.6.28) seems to fix these issues
> reliably. Rediff/ backport below, tested under the circumstances above and 
> hopefully correct.

It turns out that this patch isn't sufficient.  Additional changes are 
needed, as posted here:

	http://marc.info/?l=linux-usb&m=123196296431175&w=2

In principle these two patches should be combined into a single one.  
Unfortunately the new patch has not yet even been submitted for 
mainline, let alone accepted, so it can't go into a stable kernel.

Alan Stern

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