Hello,

In 2.6.16-rc6 (probably in earlier rc as well),
following build error occurs with CONFIG_SYSFS=n.

kernel/built-in.o(.data+0x1d40): undefined reference to `uevent_helper'
lib/lib.a(kobject_uevent.o)(.text+0x5c1): In function `kobject_uevent':
/build/rc6/source/lib/kobject_uevent.c:152: undefined reference to `uevent_seqnum'
lib/lib.a(kobject_uevent.o)(.text+0x5d0):/build/rc6/source/lib/kobject_uevent.c:152: undefined reference to `uevent_seqnum'
lib/lib.a(kobject_uevent.o)(.text+0x901):/build/rc6/source/lib/kobject_uevent.c:182: undefined reference to `uevent_helper'
lib/lib.a(kobject_uevent.o)(.text+0x910):/build/rc6/source/lib/kobject_uevent.c:182: undefined reference to `uevent_helper'

This seems to be caused by mismatch of build condition.
uevent_seqnum and uevent_helper are conditional to CONFIG_SYSFS.
While they are referenced if CONFIG_HOTPLUG (and CONFIG_NET) is enabled.

Attached patch consolidates them to CONFIG_HOTPLUG && CONFIG_NET.

I tried with (!CONFIG_NET && CONFIG_SYSFS) and
(CONFIG_NET && !CONFIG_SYSFS).
Both built ok.
So I think it doesn't conflict with "[PATCH] kobject_uevent CONFIG_NET=n
fix" which is in 2.6.16-rc6.

Thanks,
-- 
Jun'ichi Nomura, NEC Solutions (America), Inc.