Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965770AbbBDVkH (ORCPT ); Wed, 4 Feb 2015 16:40:07 -0500 Received: from out1134-250.mail.aliyun.com ([42.120.134.250]:33543 "EHLO out1134-250.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932745AbbBDVkE (ORCPT ); Wed, 4 Feb 2015 16:40:04 -0500 X-Greylist: delayed 121975 seconds by postgrey-1.27 at vger.kernel.org; Wed, 04 Feb 2015 16:40:04 EST X-Alimail-AntiSpam: AC=CONTINUE;BC=0.08133885|-1;FP=0|0|0|0|0|-1|-1|-1;HT=r41g03019;MF=gang.chen@sunrus.com.cn;PH=DS;RN=9;RT=9;SR=0; Message-ID: <54D29379.8050104@sunrus.com.cn> Date: Thu, 05 Feb 2015 05:47:37 +0800 From: Chen Gang S User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.10; rv:31.0) Gecko/20100101 Thunderbird/31.4.0 MIME-Version: 1.0 To: Marcel Holtmann , Sergei Shtylyov CC: David Laight , "Gustavo F. Padovan" , Johan Hedberg , "David S. Miller" , "linux-bluetooth@vger.kernel.org" , "netdev@vger.kernel.org" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH v2] net: bluetooth: hci_sock: Use 'const void *' instead of 'void *' for 2nd parameter of hci_test_bit() References: <54CFE8BE.5030700@sunrus.com.cn> <063D6719AE5E284EB5DD2968C1650D6D1CADA5E1@AcuExch.aculab.com> <54D27D68.7040501@cogentembedded.com> <0AB99BEA-C379-439C-AD80-5F2122AE37E5@holtmann.org> In-Reply-To: <0AB99BEA-C379-439C-AD80-5F2122AE37E5@holtmann.org> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1410 Lines: 35 On 2/5/15 05:09, Marcel Holtmann wrote: > Hi Sergei, > >>>> -static inline int hci_test_bit(int nr, void *addr) >>>> +static inline int hci_test_bit(int nr, const void *addr) >>>> { >>>> return *((__u32 *) addr + (nr >> 5)) & ((__u32) 1 << (nr & 31)); >>>> } >> >>> Is there a 'standard' function lurking that will do the above. >>> On x86 the cpus 'bit test' instruction will handle bit numbers >>> greater than the word size - so it can be a single instruction. >> >> Of course, there's test_bit(). > > we did leave hci_test_bit in the code since there are some userspace facing API that we can not change. Remember that the origin of this code is from 2.4.6 kernel. > > So we can only change this if you can ensure not to break the userspace API. So might want to write unit tests to ensure working HCI filter before even considering touching this. > For me, we have to remain hci_test_bit(), it is for "__u32 *" (which we can not change). The common test_bit() is for "unsigned long *", in this case, I guess it may cause issue under 64-bit environments. Thanks. -- Chen Gang Open, share, and attitude like air, water, and life which God blessed -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/