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

[David Brownell <david-b@pacbell.net>]

> 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!


> > 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.


> > > 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?


> > > These are conflicting requirements. In fact you'd need _two_ scripts. One
> > > to load the driver, a second to configure the device the driver has bound
> > > to.
> >
> > You mean like the difference between /etc/hotplug/*.agent (load driver FOO)
> > and /etc/hotplug/*/FOO (configure each new device)?  :-)
> 
> 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.

- Dave



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