linux-kernel - Re: [PATCH 2.6.22] Add LED trigger to libata core

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Message-Id: <200703191211.l2JCB5MU015419@harpo.it.uu.se>
Date:	Mon, 19 Mar 2007 13:11:05 +0100 (MET)
From:	Mikael Pettersson <mikpe@...uu.se>
To:	alan@...rguk.ukuu.org.uk, htejun@...il.com
Cc:	chainsaw@...too.org, jgarzik@...ox.com, linux-ide@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2.6.22] Add LED trigger to libata core

On Mon, 19 Mar 2007 12:46:16 +0000, Alan Cox wrote:
> > > This duplicates the IDE core LED trigger in the libata core.
> > > I plan to use this by allowing PMU LED control on G5 towers. My test platform 
> > > is a PowerMac 7,3 (Dual G5 2.0GHz, June 2004) with a K2 (sata_svw) controller.
> > 
> > I think this fits better in libata-core.c::ata_qc_issue().  Can you move
> > it to there?
> 
> Gak. I'd rather it stayed out of ata_qc_issue() which is a critical path
> for performance. Our command issu is already too heavy and not all
> controllers have queueing to absorb that. How many controllers actually
> need this hook and can we not have ata_qc_issue_with_led() helpers for
> them ?

Agreed, toggling a led for each request seems excessive.

At least Promise controllers tend to have a HW-driven
activity led header, so wouldn't need SW-triggered
activity leds except maybe if some stupid system failed
to wire up the led header.

/Mikael
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