From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754049Ab1C2RdD (ORCPT ); Tue, 29 Mar 2011 13:33:03 -0400 Received: from mx1.redhat.com ([209.132.183.28]:12472 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752341Ab1C2RdB (ORCPT ); Tue, 29 Mar 2011 13:33:01 -0400 Message-ID: <4D9217BE.2040205@redhat.com> Date: Tue, 29 Mar 2011 14:32:46 -0300 From: Mauro Carvalho Chehab User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.13) Gecko/20101208 Red Hat/3.1.7-3.el6_0 Lightning/1.0b2 Thunderbird/3.1.7 MIME-Version: 1.0 To: Borislav Petkov CC: "linux-edac@vger.kernel.org" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH 05/30] amd64_edac: Cleanup chipselect handling References: <1297358133-14320-1-git-send-email-bp@amd64.org> <1297358133-14320-6-git-send-email-bp@amd64.org> <4D91F31A.7040600@redhat.com> <20110329151643.GA22419@aftab> <4D91FD1D.4070508@redhat.com> <20110329160211.GC22419@aftab> In-Reply-To: <20110329160211.GC22419@aftab> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Em 29-03-2011 13:02, Borislav Petkov escreveu: > On Tue, Mar 29, 2011 at 11:39:09AM -0400, Mauro Carvalho Chehab wrote: >>>>> + * Create a contiguous bitmask starting at bit position @lo and ending at >>>>> + * position @hi. For example >>>>> + * >>>>> + * GENMASK(21, 39) gives us the 64bit vector 0x000000ffffe00000. >>>>> + */ >>>>> +#define GENMASK(lo, hi) (((1ULL << ((hi) - (lo) + 1)) - 1) << (lo)) >>>>> + >>>> >>>> This is a nice macro that could be useful outside amd64. It is probably a good >>>> idea to move it to include/linux/bitops.h. >>> >>> I'd suggest rather if you want to use it in >>> EDAC. But if we have more users, I don't have a problem with putting >>> it there (or somewhere else generic enough if people have a better >>> suggestion). >> >> Yeah, other edac drivers could benefit of using it, and also could benefit on a >> variant that would do an AND operation and shift it, something like (untested): >> >> /* >> * Create a contiguous bitmask starting at bit position @lo and ending at >> * position @hi. For example >> * >> * APPLY_BITMASK(v, 21, 39) will return the result of: >> * (v & 0x000000ffffe00000) >> 21 >> */ >> #define APPLY_BITMASK(v, lo, hi) (((v) & ((1ULL << ((hi) - (lo) + 1)) - 1) << (lo)) >> (lo)) > > The macro definition doesn't match the comment. In the comment you do a bitwise > AND first and shift the result then. The way you've written it, it does > > ((v & 0x000000000007ffff << 21) >> 21) > > you need to fixup the brackets: Ah, yes. As I said, it was untested ;) I was in the middle of reviewing lots of edac patches, but I didn't want to loose the idea, so I was quick on my reply ;) > > #define APPLY_BITMASK(v, lo, hi) (((v) & (((1ULL << ((hi) - (lo) + 1)) - 1) << (lo))) >> (lo)) > > Also, this doesn't only apply it but shifts too, so it should be > > #define APPLY_BITMASK_AND_SHIFT(...) Yeah, that name sounds better ;) > > But this macro gets too special to put it in shared code. Ok. > >> Almost all edac drivers do something like the above, for example, to get DIMM rows/cols/banks, etc. >> >> Probably, the most complex part is to find a nice name for it ;) >> >> Yet, I think non-edac drivers could also benefit of such macro, and, as this is not >> edac-specific, I think it would be better to add it at bitops.h. > > No, this should go into generic code only if it has users - "it might > benefit" is not strong-enough an argument for polluting generic code. > I'd leave it in edac_core.h and push it somewhere more generic only when > I need it in other subsystems. Works for me. Thanks! Mauro