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Re: devfs and USB

To: Richard Gooch <rgooch@xxxxxxxxxxxxxxx>
Subject: Re: devfs and USB
From: Johannes Erdfelt <jerdfelt@xxxxxxxxxxx>
Date: Mon, 17 Apr 2000 20:57:39 -0700
Cc: devfs@xxxxxxxxxxx
In-reply-to: <200004180338.e3I3cng27991@vindaloo.ras.ucalgary.ca>
References: <20000328144530.Z860@valinux.com> <200004130453.e3D4r9F04628@vindaloo.ras.ucalgary.ca> <20000413115522.W14581@valinux.com> <200004152255.e3FMtG425171@vindaloo.ras.ucalgary.ca> <20000417120035.Y14581@valinux.com> <200004180236.e3I2aSo27324@vindaloo.ras.ucalgary.ca> <20000417194508.G14581@valinux.com> <200004180255.e3I2toJ27552@vindaloo.ras.ucalgary.ca> <20000417200237.I14581@valinux.com> <200004180338.e3I3cng27991@vindaloo.ras.ucalgary.ca>
Sender: owner-devfs@xxxxxxxxxxx
On Mon, Apr 17, 2000, Richard Gooch <rgooch@xxxxxxxxxxxxxxx> wrote:
> 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.

Right now? major/minor issues.

We don't have enough.

The nodes I create are either too sparse or too many.

No one seems interested in actually following through in increasing the
major/minor for 2.4 and we need this working for 2.4.

Even increasing the major/minor would be a band-aid solution.

I'm much more content using a solution which is here today and IMHO a good
solution.

JE


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