I wrote:

If the usage count for the device is non-zero ide_unregister will fail
which is likely if you just pull the card out. This silent failure leads
to all kinds of problems which break the device until it's rebooted -
quite a serious bug. There is a fixme in ide-cs.c relating to this.

I've been looking into this. I think the simplest approach is to make sure 
ide_unregister() succeeds regardless of any busy/usage status.

In order to make it succeed, I found I needed to add some checks on various 
functions to see if drives were dead or interface's present. I've made a 
working patch available at http://www.rpsys.net/openzaurus/ide.patch . If 
someone who knows more about the ide system could have a look at this, I'd 
appreciate it. If a patch along these lines could be included, it would 
unbreak ide_unregister() and hence the ide_cs module.

Thanks,

Richard