[PATCH v5] introduce macro spin_event_timeout()

[Scott Wood]

Timur Tabi wrote:
> The macro spin_event_timeout() takes a condition and timeout value
> (in microseconds) as parameters.  It spins until either the condition is true
> or the timeout expires.  It returns zero if the timeout expires first, non-zero
> otherwise.
> 
> This primary purpose of this macro is to poll on a hardware register until a
> status bit changes.  The timeout ensures that the loop still terminates if the
> bit doesn't change as expected.  This macro makes it easier for driver
> developers to perform this kind of operation properly.
> 
> Signed-off-by: Timur Tabi <timur at freescale.com>
> ---
> 
> v5: ported to arch/powerpc, made it powerpc-specific, eliminated udelay

Why make it powerpc-specific?  This would be nice to have in 
arch-independent code.

-Scott