On Sun, 22 Jul 2007, Arjan van de Ven wrote:
Date: Sun, 22 Jul 2007 21:00:39 -0700
From: Arjan van de Ven <arjan@xxxxxxxxxxxxx>
To: david@xxxxxxx
Cc: LKML <linux-kernel@xxxxxxxxxxxxxxx>,
linux-pm <linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx>
Subject: Re: Power Management framework proposal
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.
And the side that implements these needs to translate them as well...
that's two translations, and information is lost in the abstract number
in the middle that doesn't mean anything
with the current implementations you instead need to know what function to
call and what the meaning of that function is. that's not documented in
any system discoverable way, you have to read the driver documentation or
code to find it.
if you don't want to make the shift with cpufreq, that's fine. it
sounds
like you are at least 90% of the way there anyway, it's not that big
a
deal, but do you think that there's value in replacing the current
ad-hoc
approach with something more structured (even if it's not this
proposal)?
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.
David Lang
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