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

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Message-ID: <op.va878jw6gp7y00@linux-r26l.site>
Date:	Fri, 16 Apr 2010 14:13:21 +0200
From:	"Marcin Derlukiewicz" <marcin@...lukiewicz.pl>
To:	samu.p.onkalo@...ia.com, 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

Dnia 16-04-2010 o 14:00:15 <samu.p.onkalo@...ia.com> napisał(a):

>
>
>> -----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
>

I think that on my system this is /sys/devices/platform/lis3lv02d/rate
but i may be wrong. Anyway it contains 40 as a number.

Marcin.
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