linux-kernel - Re: [PATCH 2/4] lis3: remove automatic shutdown of the device

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Message-ID: <20090521120825.GH2637@elf.ucw.cz>
Date:	Thu, 21 May 2009 14:08:25 +0200
From:	Pavel Machek <pavel@....cz>
To:	Éric Piel <eric.piel@...mplin-utc.net>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/4] lis3: remove automatic shutdown of the device

Hi!

> >> After measurement on my laptop, it seems that turning off the device
> >> does not bring any energy saving (within 0.1W precision). So let's keep
> >> the device always on. It simplifies the code, and it avoids the problem
> >> of reading a wrong value sometimes just after turning the device on.
> > 
> > Well, 0.1W is still quite much for cellphone etc... but as we do not
> > have any such small users in the tree, I guess this can go in...
> > 
> Yes. BTW, what I meant is that the power consumption on my laptop can be
> read with 0.1W precision. Turning on and off the device showed 0.0W
> variations. The device should using even much less than 0.1W. According
> to the documentation, it's about 2.2mW when on and 3?W when off.

2mW would be still significant on a cellphone, draining battery in cca
20 days (which is about as bad as GSM radio), but...

If cellphone user comes, he can simply recreate powersaving code...

Feel free to add 

Signed-off-by: Pavel Machek <pavel@....cz> 

to 2,3/4. ... And btw 4/4 probably could be pushed to 2.6.30. It is
trivial enough... and "new hw" support is okay even late in cycle.
									Pavel

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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