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Date:   Tue, 14 Jul 2020 15:17:39 +0200 (CEST)
From:   Jiri Kosina <jikos@kernel.org>
To:     Darren Hart <dvhart@infradead.org>
cc:     Grant Likely <grant.likely@secretlab.ca>,
        LKML <linux-kernel@vger.kernel.org>, linux-input@vger.kernel.org,
        Grant Likely <grant.likely@arm.com>,
        Darren Hart <darren@dvhart.com>,
        Benjamin Tissoires <benjamin.tissoires@redhat.com>,
        stable@vger.kernel.org
Subject: Re: [PATCH] hid-input: Fix devices that return multiple bytes in
 battery report
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On Fri, 10 Jul 2020, Darren Hart wrote:

> > Some devices, particularly the 3DConnexion Spacemouse wireless 3D
> > controllers, return more than just the battery capacity in the battery
> > report. The Spacemouse devices return an additional byte with a device
> > specific field. However, hidinput_query_battery_capacity() only
> > requests a 2 byte transfer.
> >
> > When a spacemouse is connected via USB (direct wire, no wireless dongle)
> > and it returns a 3 byte report instead of the assumed 2 byte battery
> > report the larger transfer confuses and frightens the USB subsystem
> > which chooses to ignore the transfer. Then after 2 seconds assume the
> > device has stopped responding and reset it. This can be reproduced
> > easily by using a wired connection with a wireless spacemouse. The
> > Spacemouse will enter a loop of resetting every 2 seconds which can be
> > observed in dmesg.
> >
> > This patch solves the problem by increasing the transfer request to 4
> > bytes instead of 2. The fix isn't particularly elegant, but it is simple
> > and safe to backport to stable kernels. A further patch will follow to
> > more elegantly handle battery reports that contain additional data.
> >
> 
> Applied and tested on 5.8.0-rc4+ (aa0c9086b40c) with a 3Dconnexion
> SpaceMouse Wireless (tested connected via USB). Observed the same
> behavior Grant reports before the patch. After the patch, the device stays
> connected successfully.
> 
> Tested-by: Darren Hart <dvhart@infradead.org>

Applied, thanks.

-- 
Jiri Kosina
SUSE Labs