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Subject: Re: [PATCH] 2.5.15 IDE 61
To: nconway.list@ukaea.org.uk (Neil Conway)
Date: Tue, 14 May 2002 17:46:26 +0100 (BST)
Cc: alan@lxorguk.ukuu.org.uk (Alan Cox), rmk@arm.linux.org.uk (Russell King),
        dalecki@evision-ventures.com (Martin Dalecki),
        linux-kernel@vger.kernel.org
In-Reply-To: <3CE1356A.B09C62F1@ukaea.org.uk> from "Neil Conway" at May 14, 2002 05:03:54 PM
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From: Alan Cox <alan@lxorguk.ukuu.org.uk>
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> block-layer because another request has been added, it needs to know
> that it shouldn't do anything until the DMAing finishes.  It could find
> that out by looking at a channel->busy flag.  If it doesn't use a busy
> flag, then what provides the locking?

You can either use device status information or the queue lock. It might
well be using channel->busy or queue->channel->busy type flags. However
you've now got a single queue and a single channel lock flowing through
a single function - which seems cleaner to me than splitting stuff into
multiple queues, locking them against one another and the like

> > From an abstract hardware point of view each ide controller is a queue not
> > each device. Not following that is I think the cause of much of the existing
> > pain and suffering.
> 
> Agreed.  And in the case of a cmd640 (etc.), the queue should handle
> both channels.

Yep