linux-kernel - Re: [PATCH] parport/ppdev: fix registration of sysctl entries

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Date:	Sun, 6 Jul 2008 20:00:33 +0300
From:	Eduard - Gabriel Munteanu <eduard.munteanu@...ux360.ro>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
Cc:	Al Viro <viro@...IV.linux.org.uk>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Marcin Slusarz <marcin.slusarz@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Frans Pop <elendil@...net.nl>
Subject: Re: [PATCH] parport/ppdev: fix registration of sysctl entries

On Sun, 6 Jul 2008 17:08:02 +0100
Alan Cox <alan@...rguk.ukuu.org.uk> wrote:

> > IMHO, there is one reason ppdev exists: allow both _safe_ and _raw_
> > access to the parallel port, and a much better alternative to the
> > iopl stuff.
> 
> And various devices support sharing protocols on the parallel port.

But isn't it incorrect to assume that sharing protocols allow multiple
separate users? Why not have an userspace server mux/demux requests?
Told more properly, such devices are multi-context, not multi-user.

AFAICT, this is similar to software mixing on soundcards, where we have
an additional layer mixing (~ multiplexing) outgoing PCM streams.

The parallel port itself is not designed to be shared, so even if the
device supports it, it does not mean we should allow independent
access. We really should have an userspace lib/server to do this.

	Eduard
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