linux-kernel - Re: [PATCH 28/31] iio: gyro: use parity32 in adxrs450.c

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <56F8F045.7060409@metafoo.de>
Date:	Mon, 28 Mar 2016 10:50:13 +0200
From:	Lars-Peter Clausen <lars@...afoo.de>
To:	Jonathan Cameron <jic23@...nel.org>,
	"zhaoxiu.zeng" <zhaoxiu.zeng@...il.com>,
	Michael Hennerich <Michael.Hennerich@...log.com>,
	Hartmut Knaack <knaack.h@....de>,
	Peter Meerwald <pmeerw@...erw.net>
Cc:	linux-kernel@...r.kernel.org, linux-iio@...r.kernel.org
Subject: Re: [PATCH 28/31] iio: gyro: use parity32 in adxrs450.c

On 03/28/2016 10:35 AM, Jonathan Cameron wrote:
> On 27/03/16 08:42, zhaoxiu.zeng wrote:
>> From: Zeng Zhaoxiu <zhaoxiu.zeng@...il.com>
>>
>> Signed-off-by: Zeng Zhaoxiu <zhaoxiu.zeng@...il.com>
> Interesting.  Whilst obviously correct I wonder if this obscures the
> intent of the code a little. Lars, what do you think?

The parity function is newly introduced in this series and can be more
efficient that  just hw_weight() & 1 on certain architectures. Since the
result is the same using it is certainly an improvement. But ...

[...]
>> -	if (!(hweight32(tx) & 1))
>> -		tx |= ADXRS450_P;
>> +	tx |= !parity32(tx) * ADXRS450_P;

... this should still be

if (!parity32(tx))
	tx |= ADXRS450_P;

Otherwise it's a bit too much obfuscated for my taste. Just leave it to the
compiler to optimize it as it sees it fit.