From patchwork Mon Jul 30 07:13:56 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Wang, Wei W" X-Patchwork-Id: 10548605 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 0FB9513B8 for ; Mon, 30 Jul 2018 07:43:06 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 024212838F for ; Mon, 30 Jul 2018 07:43:06 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id EA76428511; Mon, 30 Jul 2018 07:43:05 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.9 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from lists.gnu.org (lists.gnu.org [208.118.235.17]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id EFE1B284D4 for ; Mon, 30 Jul 2018 07:43:03 +0000 (UTC) Received: from localhost ([::1]:50941 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fk2pb-0006Hd-6R for patchwork-qemu-devel@patchwork.kernel.org; Mon, 30 Jul 2018 03:43:03 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:56566) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fk2oS-0005Sr-1F for qemu-devel@nongnu.org; Mon, 30 Jul 2018 03:41:52 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fk2oP-0001KT-AY for qemu-devel@nongnu.org; Mon, 30 Jul 2018 03:41:52 -0400 Received: from mga05.intel.com ([192.55.52.43]:40268) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1fk2oP-0001K9-2Y for qemu-devel@nongnu.org; Mon, 30 Jul 2018 03:41:49 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga004.fm.intel.com ([10.253.24.48]) by fmsmga105.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 30 Jul 2018 00:41:48 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.51,422,1526367600"; d="scan'208";a="75663664" Received: from devel-ww.sh.intel.com ([10.239.48.110]) by fmsmga004.fm.intel.com with ESMTP; 30 Jul 2018 00:41:46 -0700 From: Wei Wang To: qemu-devel@nongnu.org, peterx@redhat.com, dgilbert@redhat.com, quintela@redhat.com Date: Mon, 30 Jul 2018 15:13:56 +0800 Message-Id: <1532934837-5966-2-git-send-email-wei.w.wang@intel.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1532934837-5966-1-git-send-email-wei.w.wang@intel.com> References: <1532934837-5966-1-git-send-email-wei.w.wang@intel.com> X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 192.55.52.43 Subject: [Qemu-devel] [PATCH 1/2] bitmap.h: add comments to BITMAP_LAST_WORD_MASK X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: mst@redhat.com Errors-To: qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Sender: "Qemu-devel" X-Virus-Scanned: ClamAV using ClamSMTP This macro was ported from Linux and we've reached an aggreement there that the corner case "nbits = 0" is not applicable to this macro, because when "nbits = 0", which means no bits to mask, this macro is expected to return 0, instead of 0xffffffff. This patch simply adds a comment above the macro as a note to users about the corner case. Signed-off-by: Wei Wang CC: Dr. David Alan Gilbert CC: Juan Quintela CC: Peter Xu --- include/qemu/bitmap.h | 1 + 1 file changed, 1 insertion(+) diff --git a/include/qemu/bitmap.h b/include/qemu/bitmap.h index 509eedd..f53c640 100644 --- a/include/qemu/bitmap.h +++ b/include/qemu/bitmap.h @@ -60,6 +60,7 @@ */ #define BITMAP_FIRST_WORD_MASK(start) (~0UL << ((start) & (BITS_PER_LONG - 1))) +/* "nbits = 0" is not applicable to this macro. Callers should avoid that. */ #define BITMAP_LAST_WORD_MASK(nbits) (~0UL >> (-(nbits) & (BITS_PER_LONG - 1))) #define DECLARE_BITMAP(name,bits) \