Date: Wed, 10 Dec 2008 09:16:40 +0100
From: Joerg Dorchain <joerg@dorchain.net>
To: linux-m68k@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] amiflop: get rid of sleep_on calls
Message-ID: <20081210081640.GG30213@Redstar.dorchain.net>
References: <1228755578-26069-1-git-send-email-aeb@debian.org> <20081209082608.GA10651@Redstar.dorchain.net> <20081210004810.GA5073@infernal.debian.net>
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On Wed, Dec 10, 2008 at 01:48:10AM +0100, Andreas Bombe wrote:
> I think we're not talking about the same problem.  If I were to use
> complete() together with wait_for_completion() there would be a problem
> if fd_motor_on() can get as far as wait_for_completion() while a
> previous completion is yet uncompleted.  This can not happen for
> different drives, as the fd_select() would block.  If it could happen
> for the same drive, the complete() would allow only one task to
> continue.  The complete_all() takes care of that.
>=20
> If requests are serialized for a drive so that there won't ever be two
> running at the same time for certain (thinking about it, it's probable),
> I could make it a simple complete().  It's hardly worth the risk,
> however.

IIRC (have not touched the driver for quite some time) at a
certain stage all requests for a specific drive are serialized.
The amiga floppy drives read and write whole tracks only, so
follow-up acesses are likely to be on the same track and then
served from the buffer of decoded blocks. I you do wild track
jumping, it is slower than the original AmigaOS-driver.

But as I am not sure, and floppy drives are slow anyway, the
complete_all() won't give any notable performance penalty, I guess.

Joerg

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