linux-kernel - Re: [PATCH] Driver Core: devtmpfs - kernel-maintained tmpfs-based /dev

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Message-ID: <20090811213128.2f2a3093@infradead.org>
Date:	Tue, 11 Aug 2009 21:31:28 -0700
From:	Arjan van de Ven <arjan@...radead.org>
To:	Greg KH <greg@...ah.com>
Cc:	David Dillow <dave@...dillows.org>,
	Andi Kleen <andi@...stfloor.org>, Greg KH <gregkh@...e.de>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	linux-kernel@...r.kernel.org, Kay Sievers <kay.sievers@...y.org>,
	Jan Blunck <jblunck@...e.de>, Harald Hoyer <harald@...hat.com>,
	Scott James Remnant <scott@...ntu.com>
Subject: Re: [PATCH] Driver Core: devtmpfs - kernel-maintained tmpfs-based
 /dev

On Tue, 11 Aug 2009 17:34:33 -0700
Greg KH <greg@...ah.com> wrote:

> On Tue, Aug 11, 2009 at 08:25:27PM -0400, David Dillow wrote:
> > On Tue, 2009-08-11 at 16:55 +0200, Andi Kleen wrote:
> > > > No, not really. It isn't hard to make a static /dev, or a
> > > > rescue initrd for the cases with dynamic device numbers.
> > > 
> > > There's a world between strictly controlled embedded and fully
> > > general distributions.
> > 
> > Sure, and I've acknowledged that. But it doesn't mean this needs a
> > kernel solution.
> > 
> > > I want a dynamic /dev, but a fast one that doesn't need initrd or
> > > slows down booting.
> > 
> > So use Eric/Arjan's program that does it in 60ms -- you get a
> > dynamic /dev, no initrd, fast boot, and no kernel changes required.
> 
> Their program only handles it for a reconstruction of /dev based on
> sysfs one time at boot.  It does not handle things that are added or
> discovered by the system after that, you need udev for that.
> 
> So it's a great hack for boot time stuff, but not a complete /dev
> management replacement 

yeah you want udev for that anyway for various reasons...
(not that udev is expensive per se, the expensive part of it is the exec
of modprobe a hundred times... beyond that udev seems pretty cheap to
me)



-- 
Arjan van de Ven 	Intel Open Source Technology Centre
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