[i2c] [patch 2.6.24-rc5-git] add i2c_new_dummy() utility

[David Brownell]

On Saturday 29 December 2007, David Brownell wrote:
> I still don't know why you get lockdep warnings and I don't ...

Theory:  my test systems were turning lockdep off because of
a lockdep (usage) deficiency that triggers while booting:

	enable_irq_wake(GPIO_irq)
		holds irq_desc[GPIO_irq].lock
		and calls
	enable_irq_wake(parent_of(GPIO_irq))
		which grabs irq_desc[parent_of(GPIO_irq))]

Lockdep falsely detects that as a potential recursion, and
then turns off all further lockdep calls.

I think a genirq patch to make set_irq_chained_handler()
put the parent into a different locking class may help
resolve that issue.

- Dave