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Re: devfs and USB

To: devfs@xxxxxxxxxxx
Subject: Re: devfs and USB
From: Richard Gooch <rgooch@xxxxxxxxxxxxxxx>
Date: Mon, 17 Apr 2000 21:38:49 -0600
In-reply-to: <20000417200237.I14581@xxxxxxxxxxx>
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Sender: owner-devfs@xxxxxxxxxxx
Johannes Erdfelt writes:
> On Mon, Apr 17, 2000, Richard Gooch <rgooch@xxxxxxxxxxxxxxx> wrote:
> > Johannes Erdfelt writes:
> > > On Mon, Apr 17, 2000, Richard Gooch <rgooch@xxxxxxxxxxxxxxx> wrote:
> > > > Hm. But is it quite like this? If you have a device with multiple
> > > > interfaces, and multiple drivers get loaded, what's the interface to
> > > > user-space? Do you have a single device node and multiplex that, or do
> > > > you actually present multiple device nodes, with each hooked to a
> > > > single driver?
> > > 
> > > Right now, we have one node for the entire device and everything is
> > > done via ioctl()'s. This isn't a good idea. I have a solution which
> > > splits out everything into separate nodes, but I'm still
> > > implementing some of it.
> > 
> > Yeah, I think separate device nodes would be cleaner. Now, if you do
> > that, do you still need the user-space daemon talking via the
> > dynamically created "generic" device node? Or can you just talk via a
> > central device node for all USB devices?
> > 
> > The PCMCIA code, for example, just as a central node/pipe which
> > cardmgr talks to. Why can't you do it like that?
> 
> This the same interface that user level drivers will use.
> 
> We could use a central node/pipe, but we're gonna create the device
> nodes anyway, so might as well use them.

Why are you creating these "generic" device nodes anyway?

What I'm basically trying to work out is why you can't have a central
pipe which the daemon talks to, and when drivers attach to the
interface, the daemon talks to the USB subsystem and does a mknod(2)
as appropriate. This is the kind of argument the anti-devfs crowd will
make.

                                Regards,

                                        Richard....
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