Date: Mon, 2 Jun 2008 11:16:44 -0700
From: Kristen Carlson Accardi <kristen.c.accardi@intel.com>
To: Jeff Garzik <jeff@garzik.org>
Cc: Mark Lord <liml@rtr.ca>, Alan Cox <alan@lxorguk.ukuu.org.uk>,
       Pavel Machek <pavel@ucw.cz>, Theodore Tso <tytso@mit.edu>,
       linux-ide@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] ata: ahci: power off unused ports
Message-ID: <20080602111644.54738d57@appleyard>
In-Reply-To: <484438BF.7070303@garzik.org>
References: <20080508161008.59361de5@appleyard>
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	<20080527143202.4bab5bf0@appleyard>
	<20080527225926.GE6843@mit.edu>
	<20080527163251.04054a74@appleyard>
	<20080531080015.GG5405@ucw.cz>
	<4842F5A8.9020708@garzik.org>
	<20080602080440.25fc663c@core>
	<4843A4A7.3020809@garzik.org>
	<4843EF88.2040606@rtr.ca>
	<48441AA6.8080704@garzik.org>
	<20080602100019.3d2d2522@appleyard>
	<484431AB.7010005@garzik.org>
	<20080602104753.3f24087d@appleyard>
	<484438BF.7070303@garzik.org>
Reply-To: kristen.c.accardi@intel.com
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On Mon, 02 Jun 2008 14:15:27 -0400
Jeff Garzik <jeff@garzik.org> wrote:

> Kristen Carlson Accardi wrote:
> > Here you can see that it would be very easy for another driver
> > to just add code to set the NO_HOTPLUG flag and then this code
> > will work for them as well, since we power off the phy using
> > DET which is specified by SATA.
> 
> > here's that code:
> 
> Agreed.  The main discussion in this sub-thread is more about user 
> interface.  The user interface in this case, a module option, is 
> specific to AHCI.
> 
> Surely you can see how it is a bit silly to force each driver writer to 
> create the same user interface in each driver, to support a generic concept.
> 
> 	Jeff
> 
> 
Not all drivers will need a user interface to turn off hotplug
I would think.  At any rate - I would think it'd be better to let
driver writers decide how they want their drivers to behave wrt
hotplug and power instead of forcing a generic policy on everyone.

This patch would provide users of AHCI controllers a way to save
power now, while you work on the grand scheme for polling/turning on off
hotplug via sysfs.  It's an interim solution that impacts nobody but
ahci users and is can be easily integrated into whatever solution you
eventually work out.


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