linux-kernel - RE: [PATCH] lis3lv02d: provide means to disable polled input interface

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Date:	Fri, 16 Apr 2010 14:00:15 +0200
From:	<samu.p.onkalo@...ia.com>
To:	<marcin@...lukiewicz.pl>, <jkosina@...e.cz>,
	<eric.piel@...mplin-utc.net>
CC:	<akpm@...ux-foundation.org>, <pavel@....cz>,
	<lm-sensors@...sensors.org>, <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] lis3lv02d: provide means to disable polled input
 interface



>-----Original Message-----
>From: ext Marcin Derlukiewicz [mailto:marcin@...lukiewicz.pl]
>Sent: 16 April, 2010 14:42
>To: Jiri Kosina; Éric Piel
>Cc: Andrew Morton; Onkalo Samu.P (Nokia-D/Tampere); Pavel Machek; lm-
>sensors@...sensors.org; linux-kernel@...r.kernel.org
>Subject: Re: [PATCH] lis3lv02d: provide means to disable polled input
>interface
>
>Dnia 09-04-2010 o 15:32:59 Jiri Kosina <jkosina@...e.cz> napisał(a):
>
>> On Fri, 9 Apr 2010, Éric Piel wrote:
>>
>>> > This is reported to create 20% CPU usage increase (and
>proportionaly
>>> higher
>>> > power consumption) just for the ipolldevd kernel thread (which is
>used
>>> > to read the sensor).
>>> >
>>> > As most users probably only use the freefall functionality of the
>>> driver
>>> > and not the joystick interface, provide means for disabling the
>>> registration
>>> > of joystick device altogether via module parameter.
>>> > (I'd rather make it default to 0, but this will break backwards
>>> compatibility).
>>> Are you saying there is a 20% CPU usage even when the joystick
>interface
>>> is not open? This should not happen (and this is not happening on my
>>> laptop). The polling should happen only when a userspace app opens
>the
>>> joystick interface (like running neverball).
>>>
>>> So I'd tend to think it's more due to a misconfiguration of the
>system
>>> (like xserver using the joystick interface as a pointer device) or
>it's
>>> a bug in the way we set up the polling. Could you investigate and let
>me
>>> know?
>>
>> Marcin originally reported this to me.
>>
>> Marcin, could you please check 'lsof' output to see whether the
>joystick
>> interface has been open by some application?
>>
>> Thanks,
>>
>
>sorry for the delay, had a crunch time
>
>here is the link for this lsof:
>https://bugzilla.novell.com/attachment.cgi?id=354953
>

Could you check what is the polling period of the device.
something like:
cat /sys/devices/platform/lis3lv02d/input/input9/poll

it is current polling period in milliseconds. 0 disables polling.

-Samu