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

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Message-ID: <20100409201110.5d75a24e@hyperion.delvare>
Date:	Fri, 9 Apr 2010 20:11:10 +0200
From:	Jean Delvare <khali@...ux-fr.org>
To:	Jiri Kosina <jkosina@...e.cz>
Cc:	Éric Piel <eric.piel@...mplin-utc.net>,
	Marcin Derlukiewicz <marcin@...lukiewicz.pl>,
	linux-kernel@...r.kernel.org, lm-sensors@...sensors.org,
	Pavel Machek <pavel@....cz>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [lm-sensors] [PATCH] lis3lv02d: provide means to disable polled
  input interface

On Fri, 9 Apr 2010 15:32:59 +0200 (CEST), Jiri Kosina wrote:
> 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?

I would randomly blame hal. It keeps my IR remote control device opened
all the time and I have no idea why.

-- 
Jean Delvare
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