From: Pavel Roskin <proski@gnu.org>

The "ide-cs" module cannot be unloaded because it uses obsolete
MOD_INC_USE_COUNT and MOD_DEC_USE_COUNT macros.  In fact, they are not
needed in ide-cs.c in 2.6 kernels.  The generic PCMCIA code already
increases use count for every device served by the driver, so it's
impossible to unload the ide-cs driver while it's in use.

I was told that the removal of IDE interfaces may be unsafe in 2.6
kernels.  However, MOD_INC_USE_COUNT only prevents removal of the module,
not the interface.  It's also the first obstacle, albeit a trivial one,
for anybody debugging those problems (i.e. loading a modified module
requires "rmmod -f" or reboot to unload the old version).