Re: __bad_udelay in 2.2.18pre15

From: Ralf Baechle (
Date: Wed Oct 11 2000 - 11:05:22 EST

On Wed, Oct 11, 2000 at 12:13:48PM +0200, Benjamin Herrenschmidt wrote:

> >Well, at first, I wanted to implement it the same way on PPC. However, it
> >dies on all occurences where udelay is called with a non-constant expression.
> >
> >I spotted this case in a few PPC specific stuffs (fixable), but also in
> >the sys_nanosleep code, and in the de4x5 driver.
> Hrm... looks like I missed the story about the __builtin_constant_p(). Is
> this a gcc-specific built-in feature ?

Like all __builtin_* functions. It returns 1 if the compiler is able to
figure out that the argument is a constant expression, 0 otherwise. See
include/asm-i386/io.h for particular beautyfull examples ...

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