[maemo-users] brightness Re: [maemo-users] Re: Storage/Sleep Issues..

From: James Sparenberg james at linuxrebel.org
Date: Fri Jan 26 00:48:58 EET 2007
On Thursday 25 January 2007 04:38, Igor Stoppa wrote:
> On Thu, 2007-01-25 at 13:08 +0100, ext Frantisek Dufka wrote:
> > Igor Stoppa wrote:
> > >> I thought it can be half of power
> > >> consumption on such devices. It was like that on ipaq 3870 I had. I
> > >> remeber something like 80mA when display off ~130mA minimum brightness
> > >> ~200mA full brightness, ~300mA full brightness + 100%CPU (not sure
> > >> about exact values, it is long time ago, it was available as file in
> > >> /proc in Familiar linux). On N770 I cannot check easily since some
> > >> parts of power management is ... guess what? There is this myth about
> > >> hidden power management ;-)
> > >
> > > Nothinig prevents you from creating a sysfs entry wich returns
> > >
> > > tahvo_get_backlight_level()
> > >
> > > or even a proc one, if you really are into that sort of thing.
> >
> > There is such entry - /sys/devices/platform/omapfb/panel/backlight_level
> >
> > I meant way to get discharge current from battery circuit to know what
> > is actual consumption of the device and how big is the influence of
> > various parts. This is easy to get on laptops and it was possible on
> > iPAQ but is currently kept very close to Nokia's chest.
> I think you won't see this information made available anytime soon for a
> very good reason: there is a significant risk that somebody uses this
> knowledge to write malicious software that literally blows the device by
> doing nasty thinigs with the battery and Nokia would be liable if it was
> releasing such information. This is also behind the clause about reverse
> engineering.
> One has to prove that we made it hard for him to get such information,
> so that we are not liable when he blows hiimself up with a modified
> 770/n800.

I'm sorry but if the above were a valid reason then I would highly recommend 
that Nokia shut down it's doors.  No amount of effort on Nokia's part will 
halt malicious lawsuits.  Period.

Further the above is invalid if not only because you are using OSS as your 
base and it is governed by a legally tested license, but also because people 
are asking for access to public information not anything proprietary and 
bound by NDA's.  If you are modifying OSS and choose intentionally to refuse 
to divulge modifications to this software please let me know.  


> >  Yes one can
> > measure it but it would need some tools, reading some register is much
> > easier. Would be also good guide for programmers implementing proper
> > idle state.
> We are tryinig to figure out something similar, without risk.
> But your statement is mostly for kernel side. Applications can use the
> methods already described.
> > I would be interested in difference betwen SD/MMC vs internal flash I/O
> > (i.e. how does rootfs on MMC affect battery life) but other things are
> > equally interesting to know (wlan transmit/receive, sound, DSP on, DSP
> > vs main CPU doing similar stuff ...).
> It requires a little hw hacking, but you can measure them quite easily
> with a good enough power meter (precise to mA) and some wiring.

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