linux-kernel - Re: USB keyboard backlight powering down.

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Message-ID: <20121017125538.GA2934@hansolo.jdub.homelinux.org>
Date:	Wed, 17 Oct 2012 08:55:39 -0400
From:	Josh Boyer <jwboyer@...hat.com>
To:	Sarah Sharp <sarah.a.sharp@...ux.intel.com>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Michael Spang <spang@...gle.com>, linux-usb@...r.kernel.org,
	Dave Jones <davej@...hat.com>,
	Michael Spang <spang@...omium.org>,
	Linux Kernel <linux-kernel@...r.kernel.org>, greno@...izon.net,
	Fedora Kernel Team <kernel-team@...oraproject.org>
Subject: Re: USB keyboard backlight powering down.

On Tue, Oct 16, 2012 at 10:35:24AM -0700, Sarah Sharp wrote:
> On Tue, Oct 16, 2012 at 09:54:36AM -0700, Greg Kroah-Hartman wrote:
> > On Tue, Oct 16, 2012 at 12:45:56PM -0400, Michael Spang wrote:
> > > On Tue, Oct 16, 2012 at 11:20 AM, Dave Jones <davej@...hat.com> wrote:
> > > > Gerry (CC'd) reported a bug to us that since 3.6.1, his illuminated
> > > > Logitech USB keyboard doesn't light up until he hits a key, and then
> > > > it immediately powers back off, defeating the purpose of having an
> > > > illumated keyboard.
> > > >
> > > > Looking over the 3.6.1 changelog, I see this change, which sounds
> > > > like it might be responsible ?
> > > >
> > > > commit ee537508bdc0c00b96ac497f3d82a68f820e6182
> > > > Author: Michael Spang <spang@...omium.org>
> > > > Date:   Fri Sep 14 13:05:49 2012 -0400
> > > >
> > > >     Increase XHCI suspend timeout to 16ms
> > > 
> > > I don't think this is related to your problem, as this patch is in
> > > suspend/resume code. It just allows the controller more time to halt.
> > 
> > Yeah, that looks odd.
> > 
> > But, (adding linux-usb@...r), I think we enabled some "put the device to
> > sleep if it is idle" logic for all devices, which is what is looking
> > like is happening here.  The keyboard is being told to go to sleep in
> > order to save power.
> > 
> > We are saving more power, but it looks like the user wants to disable
> > it, which makes sense for this device.
> > 
> > So, do we do this from within the kernel with a blacklist, or rely on
> > the user knowing how to poke the proper sysfs file to turn the keyboard
> > back on?
> 
> This was the udev bug I was referring to, which I think is causing the
> keyboard to have auto-suspend enabled:
> 
> https://bugzilla.redhat.com/show_bug.cgi?id=825284
> 
> udev shouldn't be enabling auto-suspend of USB hids by default, since
> many of them don't send a wakeup to come out of suspend when they
> should.  For example, most USB mice only send a wakeup even when they
> are clicked, not when they are moved.  That causes the user to sit
> there, frustrated, as they move their mouse and wonder why their screen
> doesn't unblank.  Other keyboards also lose keystrokes, which means if
> you pause to compose your thoughts, the first couple letters you type
> gets dropped.

I know we fixed that bug for F17, F18, and rawhide.  I did it myself.
I don't think this is udev related, but we'll double check the version.

Gerry, are you using udev-182-3.fc17 or newer on your F17 install?

josh
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