xorg-devel Digest, Vol 57, Issue 17

Kristen Accardi kaccardi at gmail.com
Sun Oct 6 13:41:23 PDT 2013

On Oct 6, 2013 1:26 PM, "Gene Mosher" <gene at viewtouch.com> wrote:
> On 10/06/2013 12:00 PM, xorg-devel-request at lists.x.org wrote:
>> Message: 2
>> Date: Sun, 06 Oct 2013 11:17:13 -0700
>> From: Keith Packard <keithp at keithp.com>
>> To: Mark Kettenis <mark.kettenis at xs4all.nl>
>> Cc: xorg-devel at lists.freedesktop.org, kaccardi at gmail.com,
>> arjan at linux.intel.com
>> Subject: Re: [PATCH] Close non-keyboard devices on DPMS off
>> Message-ID: <86siwe463a.fsf at miki.keithp.com>
>> Content-Type: text/plain; charset="utf-8"
>> Mark Kettenis <mark.kettenis at xs4all.nl> writes:
>>> > Is that really desirable?
>> It has a couple of benefits -- the first is that touch screens and touch
>> pads often get input while your laptop screen is closed; this prevents
>> that from waking up the X server.
>> The second is that turning off input devices can allow the system to
>> shut down USB resources and save a bunch of power. I posted the patch so
>> that we could get measurements of the power savings.
>>> > For me, moving the mouse has always been the most natural way to wake
>>> > up the screen.
>> Yeah, that's the usual way I wake my machine up as well. However, if you
>> try this on an OS X machine, you'll find that only the keyboard will
>> wake the machine up. So, it's not a universal policy at least.
>>> > And I can imagine that touching the screen is the most
>>> > natural way to do it on a device with a touchscreen.  Such devices
>>> > might not even have keyboard.
>> It's hard to imagine a device without *any* keys, but it's certainly
>> possible. The trick would be to figure out how to detect this
>> automatically; my machine lists six "keyboard" devices:
>>     ? Power Button                            id=6 [slave  keyboard (3)]
>>     ? Power Button                            id=8 [slave  keyboard (3)]
>>     ? Sleep Button                            id=9 [slave  keyboard (3)]
>>     ? FaceTime HD Camera (Built-in)           id=11 [slave  keyboard (3)]
>>     ? Apple Inc. Apple Internal Keyboard / Trackpad id=12 [slave
keyboard (3)]
>>     ? Video Bus                               id=7 [slave  keyboard (3)]
>> I think the interesting part here is the potential for power savings
>> while the screen is blanked; getting some idea of how much closing the
>> other devices is worth would be really helpful in figuring out when to
>> make this choice.
>> --
>> keith.packard at intel.com
> Keith, why do you want to fix something that isn't broken, by breaking
it?  You say it's hard to imagine a device without *any* keys, well such
'devices' are the ONLY kind of devices I ship running the X server.  These
are not battery operated machines so the advantage of saving power doesn't
exist.  What is wrong with waking up a touchscreen driven computer by
touching the screen?  There's nothing wrong with it!
> --Gene Mosher

You should always try to save power, even if you are using electricity
instead of a battery.  Its the right thing to do.
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