linux-kernel - Re: [PATCH] powerpc: sysdev: cpm1: Optimise gpio bit calculation

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Date:   Fri, 10 Mar 2017 07:06:30 -0600
From:   Segher Boessenkool <segher@...nel.crashing.org>
To:     Christophe LEROY <christophe.leroy@....fr>
Cc:     Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Scott Wood <oss@...error.net>, linuxppc-dev@...ts.ozlabs.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] powerpc: sysdev: cpm1: Optimise gpio bit calculation

On Fri, Mar 10, 2017 at 11:54:19AM +0100, Christophe LEROY wrote:
> gpio_get() and gpio_set() are used extensively by some GPIO based 
> drivers like SPI, NAND, so it may be worth it as it doesn't impair 
> readability (if anyone prefers, we could write  (1 << 31) >> i  instead 
> of  0x80000000 >> i )

1 << 31 is undefined behaviour, of course.


Segher