Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1754395AbcCOVue (ORCPT <rfc822;w@1wt.eu>);
	Tue, 15 Mar 2016 17:50:34 -0400
Received: from mout.kundenserver.de ([212.227.126.131]:62036 "EHLO
	mout.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S1753138AbcCOVu3 (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Tue, 15 Mar 2016 17:50:29 -0400
From: Arnd Bergmann <arnd@arndb.de>
To: Hartley Sweeten <HartleyS@visionengravers.com>
Cc: Ian Abbott <abbotti@mev.co.uk>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Amitoj Kaur Chawla <amitoj1606@gmail.com>,
        Bhaktipriya Shridhar <bhaktipriya96@gmail.com>,
        "devel@driverdev.osuosl.org" <devel@driverdev.osuosl.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] staging/comedi/dt282x: avoid integer overflow warning
Date: Tue, 15 Mar 2016 22:50:16 +0100
Message-ID: <3577040.FW0X5IMTpl@wuerfel>
User-Agent: KMail/4.11.5 (Linux/3.16.0-10-generic; KDE/4.11.5; x86_64; ; )
In-Reply-To: <BN3PR0101MB1057ABAE207C199306C431C0D0890@BN3PR0101MB1057.prod.exchangelabs.com>
References: <1457995713-1517950-1-git-send-email-arnd@arndb.de> <BN3PR0101MB1057ABAE207C199306C431C0D0890@BN3PR0101MB1057.prod.exchangelabs.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 7Bit
Content-Type: text/plain; charset="us-ascii"
X-Provags-ID: V03:K0:7NPIfBQb9ZXM6RizpkUkLD6dzz9qb4f47w+uGPWQKdLbSnrE299
 bTPt3YOmfxxn+p7nCxahySoZuVWCQX/Kz+eYmTckT5wY80tJz9XPwVZw4/LHc1hIkFq7rgq
 4CdK6iLFASsLzOO3s1G8GticSdxkHuFrqBoiGQTM5R8bHIu/he/tYOXPppkMLHK1ku3ucNI
 PD+Wk2Y4axiTePoXXOTgw==
X-UI-Out-Filterresults: notjunk:1;V01:K0:PbI6LlYG/YU=:bJIOMvLgarkzWklypV6IQR
 O6TCjFeFIIjAefWkw69iLPc4d7tSO4w0sU4M2NCVbCE/HkHxlhSmtg7J6axRodjMLnSlubGjg
 ycZ2gwwOBIfL/OYSnmcHPUEOlTAHX6mFXjw7UcM0/CHLpzaxl4fByoxvLExPCKFr58Jrq20qO
 9IbBgSL37sBcQo/8Ayw+ItTXgWMHawEQr+q7PkkD0wKDzPhUcXfIO5FL/+aq79b6NmojOuzNd
 R2+SGPfNAPNxSv6GFh8bZMuFe8NIh5RiydqDlOtqnIQydcdwDkq3HHeJzjUF0m4qyivo954Fb
 +V/lckvkQDL72BRILYzSdmCxNHjyFMkY7vT1scIvUpnQbh4wHNriGqwZqhcn7oVFksVybQKee
 9047hqRFO+xTXvEEX64efa84lF1IBTEB3ekL23Vz9xFPQUjkZZUYdJEsJhpoEIj5W/D5unl+u
 7FBIX001sjM/muUF1zy8kJ7fOOnLo2B6+SGQqcT0RhJEyI2xMpqIjddVqsRZG1CEFWfzkSzMN
 P8UdIV2mRG3Fgqd9N13UEHRLSYFNzUW6Q4mo5UpkumzH+K0kxt8VXY4mQWNxEMyrX5Jtypz9i
 iXfWGD3XN0ok4MHjXRHkMLHo9JIyQdUmiffbvNs4S3CO/EhOe4+eKrpSH1DR0Xqh0s4DyMiJ8
 JCuh3wCFBTH+4SqBvy47F+9De9iU+iE+8xCWN5oE28/bMyZqjmOp/weql7r6108chzau8tVUp
 shT6RrY9ZHkPHeX0
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org
Content-Length: 1523
Lines: 42

On Tuesday 15 March 2016 21:35:40 Hartley Sweeten wrote:
> On Monday, March 14, 2016 3:48 PM, Arnd Bergmann wrote:
> > gcc-6 warns about passing negative signed integer into swab16()
> > in the dt282x driver:
> 
> <snip>
> 
> > The warning makes sense, though the code is correct as far as I
> > can tell.
> >
> > This disambiguates the operation by making the constant expressions
> > we pass here explicitly 'unsigned', which helps to avoid the warning.
> >
> > Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> > ---
> >  drivers/staging/comedi/drivers/dt282x.c | 62 ++++++++++++++++-----------------
> >  1 file changed, 31 insertions(+), 31 deletions(-)
> >
> > diff --git a/drivers/staging/comedi/drivers/dt282x.c b/drivers/staging/comedi/drivers/dt282x.c
> > index 40bf00984fa5..d4d45c759c62 100644
> > --- a/drivers/staging/comedi/drivers/dt282x.c
> > +++ b/drivers/staging/comedi/drivers/dt282x.c
> > @@ -69,48 +69,48 @@
> >   * Register map
> >   */
> >  #define DT2821_ADCSR_REG		0x00
> > -#define DT2821_ADCSR_ADERR		(1 << 15)
> > -#define DT2821_ADCSR_ADCLK		(1 << 9)
> > -#define DT2821_ADCSR_MUXBUSY		(1 << 8)
> > -#define DT2821_ADCSR_ADDONE		(1 << 7)
> > -#define DT2821_ADCSR_IADDONE		(1 << 6)
> > +#define DT2821_ADCSR_ADERR		(1u << 15)
> 
> Changing all of these to use the BIT() macro should also avoid the warning.

Yes, but it won't work for the ones that have more than one bit:

#define DT2821_SUPCSR_DS_AD_TRIG       (3 << 10)

I considered using BIT() but decided against it for consistency.

	Arnd