linux-kernel - Re: Power Management framework proposal

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Date:	Sun, 29 Jul 2007 15:00:07 -0700 (PDT)
From:	david@...g.hm
To:	Pavel Machek <pavel@....cz>
cc:	Arjan van de Ven <arjan@...radead.org>,
	LKML <linux-kernel@...r.kernel.org>,
	linux-pm <linux-pm@...ts.linux-foundation.org>
Subject: Re: Power Management framework proposal

On Fri, 27 Jul 2007, Pavel Machek wrote:

> Hi!
>
>>>> example 1: a laptop screen
>>>>
>>>> mode  capacity power description
>>>> 0        0        0    off
>>>> 1      100      100    full brightness
>>>> 2       70       60    half power to the backlight
>>>> 3       50       35    quarter power to the backlight
>>>> 4       30       25    eighth power to the backlight
>>>> 5        5       10    backlight off.
>>>>
>>>> example 2: a front-panel display on a server (no
>>>> variable backlight
>>>> control)
>>>>
>>>> mode capacity power description
>>>> 0       0        0   off
>>>> 1     100      100   backlight on
>>>> 2      50       10   backlight off
>>>
>>>
>>> the problem is: the person who SETS these needs to know
>>> what they mean.
>>
>> that's what the description is for. this info can be
>> provided by the driver as part of the list_modes()
>> function.
>
> That's what /sys/class/backlight/ is for :-).

yes it is, and each type of device is growing it's own, incompatible, 
interfaces for controlling things like this. I was aiming to do two 
things.

1. head this off and try and get a more common api

2. simplify the confusion that there is with multiple functions needing to 
be implemented during the suspend/resume cycle by chaning them from 
independant suspend-only functions to being just part of the device 
settings

>>> as someone who wrote (part of) a power policy manager;
>>> sorry but you
>>> take away information I need, and in addition the
>>> different API's are
>>> absolutely no big deal.
>>
>> assuming that nobody else chimes in to disagree with you
>> I'll accept your judgement and drop the issue.
>
> Just for the record, I agree with Arjan here.

oh well. sorry to take up everyone's time.

David Lang
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