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Date: Wed, 12 Nov 2008 10:43:58 +0100
From: Mike Hommey <mh@glandium.org>
To: Miklos Szeredi <miklos@szeredi.hu>
Cc: tj@kernel.org, hch@infradead.org, fuse-devel@lists.sourceforge.net,
       greg@kroah.com, linux-kernel@vger.kernel.org
Subject: Re: [fuse-devel] [PATCHSET] FUSE: extend FUSE to support more operations
Message-ID: <20081112094357.GA5621@glandium.org>
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On Wed, Nov 12, 2008 at 10:36:25AM +0100, Miklos Szeredi <miklos@szeredi.hu> wrote:
> On Wed, 12 Nov 2008, Tejun Heo wrote:
> > Christoph Hellwig wrote:
> > > On Wed, Nov 12, 2008 at 05:41:18PM +0900, Tejun Heo wrote:
> > >>> emulated char devices to be char devices?  What I mean is, what would
> > >>> happen if instead of a char device /dev/dsp would be a regular file
> > >>> mounted on /dev/dsp (which implements all the necessary interfaces:
> > >>> ioctls, poll, etc)?
> > >> For most it would work, I suppose, but there are all sorts of wonky
> > >> users out in the wild (and quite a few that we don't have source access
> > >> to) and different configurations, so I think it's better to appear as
> > >> proper character device if it is a character device.  It will also help
> > >> udev and other desktop thingies deal with devices implemented in userland.
> > > 
> > > Note that mounting a char device on /dev/dsp is exactly the same as
> > > mounting a regular file on /dev/dsp - the only difference is what you
> > > set i_mode to.
> > 
> > A difference is how the device is located.  With proper character device
> > emulation, any char device node on any filesystem would work.  Not sure
> > how relevant that would be tho.
> 
> Yeah, I think it would be a bit hacky to lie about being a device with
> a specific major/minor number, when in fact we just set those in the
> stat fields, and the real char device would return ENODEV or implement
> something else.
> 
> So I'd prefer the CUSE approach if we want the file to actually look
> like a device.

You're talking about fusd, here.
http://www.circlemud.org/~jelson/software/fusd/

Mike
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