linux-kernel - Re: [PATCH 2/2] iwlwifi: add power management support -v2

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Date:	Mon, 26 Nov 2007 12:14:30 -0500
From:	Dan Williams <dcbw@...hat.com>
To:	Tomas Winkler <tomasw@...il.com>
Cc:	Miguel Botón <mboton.lkml@...il.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-wireless@...r.kernel.org, linville@...driver.com,
	yi.zhu@...el.com
Subject: Re: [PATCH 2/2] iwlwifi: add power management support -v2

On Mon, 2007-11-26 at 19:11 +0200, Tomas Winkler wrote:
> On Nov 26, 2007 6:18 PM, Miguel Botón <mboton.lkml@...il.com> wrote:
> >
> > On Saturday 17 November 2007 07:15:05 Tomas Winkler wrote:
> > > Why power management shouldn't be enabled while in AC? The semantic of this
> > > ioctls is quite unclear.
> >
> I
> > IWL_POWER_AC and IWL_POWER_BATTERY are just two power modes. IWL_POWER_AC
> > would be the default power mode when we're in AC (no power saving) and
> > IWL_POWER_BATTERY would be the default power mode when we're in battery
> > (power saving mode). That's why we set IWL_POWER_ENABLED flag with
> > IWL_POWER_BATTERY, because it is the only power mode that saves power.
> >
> > We can change to IWL_POWER_BATTERY or IWL_POWER_AC in any moment.
> >
> > This patch, depending if power management is enabled or not, sets which power
> > mode we should use, Then, it checks if we're already using this mode or not.
> >
> I'm not sure who introduced this names (lazy to look to history) but
> that's very misleading. Nothing says that while in
> AC we cannot do power saving and vice versa. This naming is scattered
> all over the code, there should be only one place where AC and BATTERY
> are  translated into appropriate (maybe configurable) power levels. We
> have 5 power levels defined for iwlwifi.

At some point everyone needs to standardize on power levels so that
userland has a hope of mapping the right state to the right power level
in the driver.  Otherwise, we get into a situation where broadcom power
levels don't map the same way iwl powerlevels do, and then we can't ever
do the right thing.

dan

> Tomas
> 
> > --
> >        Miguel Botón
> >
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