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

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

> 	Even for the more elaborate case, where, say, a user quickly
> inserts an ethernet card, removes it and then inserts a wireless
> ethernet card which might need a different initialization, my scheme
> would get it right because it does not look for existing devices until
> it has already initialized the hot plug event handling, since the only
> way that the first card could be detected is if the hot plugging
> facilties were in place in time to see its later removal and the
> insertion of the new card.

Exactly that's the problem. What do you wish to do when the replacement has 
happened after you have decided to do something to the interface, but before 
you've started your action.

Let me make a diagramm

enable hotplugging
start scanning bus
decide to assign IP to eth0
				eth0 goes away (eg leaving 802.11 zone)
				a PCMCIA ethernet card is plugged in
assign IP to eth0

The window is very small and in this case of little consequence, but for
a design it is still unacceptable.

You need to prevent any changes to the bus while you do the scanning.
Running hotplug support is not enough. You need further kernel support
to do racefree scanning. It gets worse if you take into account interference
with non hotpluggable busses (SCSI).
Therefore I suggest scanning in kernel space.

	Regards
		Oliver

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