Date: Thu, 1 Nov 2007 10:50:36 +0000
From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: Tejun Heo <htejun@gmail.com>
Cc: Jeff Garzik <jeff@garzik.org>, Jens Axboe <jens.axboe@oracle.com>,
       Daniel Drake <dsd@gentoo.org>,
       linux list <linux-kernel@vger.kernel.org>, linux-ide@vger.kernel.org
Subject: Re: "Fix ATAPI transfer lengths" causes CD writing regression
Message-ID: <20071101105036.3565decf@the-village.bc.nu>
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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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