crash in init_ipic_sysfs on efika

[Paul Mackerras]

Olaf Hering writes:

> I cant reproduce this bug on my board, but:
> 
> The global primary_ipic in arch/powerpc/sysdev/ipic.c can remain NULL if
> ipic_init() fails. init_ipic_sysfs() will crash in that case.
> 
> Something like this may fix it:

Is this needed for 2.6.25?  Is the system at all usable if ipic_init
fails?

Paul.