linux-kernel - Re: [PATCH] ata: ahci: power off unused ports

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Message-ID: <4844316B.1080405@garzik.org>
Date:	Mon, 02 Jun 2008 13:44:11 -0400
From:	Jeff Garzik <jeff@...zik.org>
To:	kristen.c.accardi@...el.com
CC:	Mark Lord <liml@....ca>, Alan Cox <alan@...rguk.ukuu.org.uk>,
	Pavel Machek <pavel@....cz>, Theodore Tso <tytso@....edu>,
	linux-ide@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ata: ahci: power off unused ports

Kristen Carlson Accardi wrote:
> On Mon, 02 Jun 2008 09:03:04 -0400
> Mark Lord <liml@....ca> wrote:
> 
>> Jeff Garzik wrote:
>>> Alan Cox wrote:
>>>>> If you are talking about SATA -- incorrect.
>>>>>
>>>>> The patch deals with policy, and the user MUST have the ability to 
>>>>> control this stuff.  Otherwise you create a situation where the user 
>>>>> might be denied hotplug use in valid cases, or similar negative 
>>>>> situations.
>>>> The policy isn't however complicated. Tejun added the stuff for forcing
>>>> cable type and mode on setup and has therefore written all the per device
>>>> setup code we might need. Alternatively a single
>>>>
>>>>     foo=1/0
>>>>
>>>> option has been fine for acpi and will do fine for this. Total additional
>>>> cost - 1 line.
>>> The key requirement is per-port control.  Ideally via hdparm or another 
>>> userspace tool, but kernel command line (module options) or sysfs would 
>>> be just fine too.  And agreed, the minimal you need is simply 1/0 for 
>>> the port's policy.
>> ..
>>
>> Btw.. hdparm-8.7 (unreleased) can grok /sys now, so that interface is
>> as good as any from a userspace viewpoint now.
>>
>> For the power-off of unused ports, the current patch still sounds
>> extremely vendor-specific (Intel).
> 
> Wrong - this patch is implemented according to the AHCI spec and
> has absolutely nothing vendor specific in it.

ITHM AHCI-specific, and not usable by non-AHCI SATA controllers -- which 
we would want in any solution.

	Jeff




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