xconfig is broken (example ppc 8xx)

[george anzinger]

To show the problem do:

make xconfig ARCH=ppc

in the "Platform support" menu "Processor Type" select "8xx" then close
the subminue with "MainMenu"

now select "Save and Exit"

This produces the following error messages:

ERROR - Attempting to write value for unconfigured variable
(CONFIG_SCC_ENET).
ERROR - Attempting to write value for unconfigured variable
(CONFIG_FEC_ENET).

The named CONFIG options are not set, nor are a few others related to
CONFIG_SCC_ENET.
(This means the on board NIC is not configured and since this is usually
a disc less system, boot fails when trying to mount "/" over nfs.)

make menueconfig ARCH=ppc  works correctly.

The problem appears to be related to these lines in
../ARCH/ppc/config.in

if [ "$CONFIG_CPU_PPC_8xx" = "y" ]; then
source arch/ppc/8xx_io/Config.in
fi

if [ "$CONFIG_CPU_PPC_8260" = "y" ]; then
source arch/ppc/8260_io/Config.in
fi

Only one of the two files is included, however, both configure the two
options mentioned in the error messages.

I think the problem is that the "wish" script builder does not allow a
CONFIG option to be configured in two different places, even if only one
of scripts should be included.

Additional info: Kernel revs tested 2.4.2, 2.4.3
If you swap the two "if" phrases above, the 8xx config works but the
8260 fails in the same way.  I.e. the last one wins.