Re: Adding PCMCIA support to the kernel tree -- developers needed.

[Oliver Neukum <Oliver.Neukum@lrz.uni-muenchen.de>]

On Mittwoch,  7. Februar 2001 22:14, David Brownell wrote:
> > But stable names don't save you from a need to serialise due to reuse.
> > In fact a stable name implies reuse, as it depends on bus location.
> > Either you get unique or you get stable names.
>
> I also said (different word, true) that the names don't invalidate
> (hence don't get reused!) while the agents operate.  There were
> two constraints I put in that "minimal" set; you' ve focussed on
> the first one!

OK. I had overlooked that.

> > > USB device "/proc/bus/usb/002/031" may be network interface "usb0".
> > > The lower level name (USB) is known before "usbnet" is loaded,
> > > but "usb0" isn't known till afterwards ... but then, USB hotplugging
> > > sees the USB name, and network hotplugging is what sees "usb0".
> >
> > True, but there's no equivalent for network hotplugging for other
> > subsystems.
>
> Yet.  The stack we're looking at today has two layers:  bus (USB, PCI),
> and "next" (network).  Printers and disks will be layered above busses;
> PCMCIA is another bus.

I see. However as soon as you take PCI into the picture, that's all
devices. It begins to look like recreating devfs.

> > > > c) You'd need to call after drivers have bound to interfaces.
> > >
> > > USB hotplug is called after the kernel gives drivers a chance to
> > > bind to interfaces.
> >
> > That's not enough.
> > The mapping between devices and nodes isn't 1:1 but 1:0-n
> > You need an agent run for every node and an agent for the device (to load
> > the driver)
>
> I think I allowed for that already in that comment of mine you had
> described as "theoretical"!   (I was trying to describe the practice
> of things in a general way ... surely that's one kind of theory.  :-)
>
> By "node" presumably you mean "filesystem node"?  Because I can't
> see the sense of a device that doesn't show up in _any_ namespace
> (filesystem, netdev, etc).  No software could access it, right?

Yes, I was refering to those things living in /dev ;-)
A device invisible to user space isn't useless.
A SCSI controller without devices attached is exactly that,
yet it has its uses later.

> > I am not sure. I think you need to call them independently.
>
> Have a look at how the USB hotplug agent works; they're called
> independently, in that the per-device setup can get called even
> if the driver hasn't been loaded.

I may be dense today. All I can see is usb.c::usb_new_device()

	Regards
		Oliver

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