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Message-ID: <20071101105036.3565decf@the-village.bc.nu>
Date: Thu, 1 Nov 2007 10:50:36 +0000
From: Alan Cox <alan@...rguk.ukuu.org.uk>
To: Tejun Heo <htejun@...il.com>
Cc: Jeff Garzik <jeff@...zik.org>, Jens Axboe <jens.axboe@...cle.com>,
Daniel Drake <dsd@...too.org>,
linux list <linux-kernel@...r.kernel.org>,
linux-ide@...r.kernel.org
Subject: Re: "Fix ATAPI transfer lengths" causes CD writing regression
O> Hmmm.... reading ide-cd.c::cdrom_pc_intr(). OIC, ide-cd is dealing with
> this problem by draining PIO after BMDMA engine is done. This is
> possible for BMDMA engines as they simply step out when the SG entries
> are exhausted; then, the interrupt handler kicks in and drains the
> left-over using PIO. This just isn't possible with more modern DMA engines.
Its not possible with old ones either - its a bug not a feature and is
why there is special casing for stuff like promise where this hangs the
chip.
Alan
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