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From: Andrew Morton <akpm@linux-foundation.org>
To: Joe Perches <joe@perches.com>
Cc: David Miller <davem@davemloft.net>,
	jiri@resnulli.us, netdev@vger.kernel.org,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] checkpatch: Add --strict preference for #defines using BIT(foo)
Date: Mon, 10 Nov 2014 15:36:47 -0800	[thread overview]
Message-ID: <20141110153647.f98f7d60fa24bf3bf7cbc215@linux-foundation.org> (raw)
In-Reply-To: <1415394939.23530.20.camel@perches.com>

On Fri, 07 Nov 2014 13:15:39 -0800 Joe Perches <joe@perches.com> wrote:

> Using BIT(foo) and BIT_ULL(bar) is more common now.
> Suggest using these macros over #defines with 1<<value.

urgh.  I'm counting eightish implementations of BIT(), an unknown
number of which are actually being used.  Many use 1<<n, some use
1UL<<N, another uses 1ULL<<n.  I'm a bit reluctant to recommend that
anyone should use BIT() until it has has some vigorous scrubbing :(

Is it actually an improvement?  If I see

#define X	(1U << 7)

then I know exactly what it does.  Whereas when I see

#define X	BIT(7)

I know neither the size or the signedness of X so I have to go look it
up.


I have no strong feelings either way, but I'm wondering what might have
inspired this change?


  parent reply	other threads:[~2014-11-10 23:36 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <1415265610-9338-1-git-send-email-jiri@resnulli.us>
     [not found] ` <1415265610-9338-10-git-send-email-jiri@resnulli.us>
     [not found]   ` <20141107.151607.480474516800359791.davem@davemloft.net>
2014-11-07 21:15     ` [PATCH] checkpatch: Add --strict preference for #defines using BIT(foo) Joe Perches
2014-11-09  9:50       ` Jiri Pirko
2014-11-09 14:22         ` Joe Perches
2014-11-10 23:36       ` Andrew Morton [this message]
2014-11-10 23:53         ` Joe Perches

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