On Wed, Nov 12, 2008 at 10:36:25AM +0100, Miklos Szeredi  wrote:

quoted text
> 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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