From patchwork Tue Apr 17 23:35:06 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Martin Wilck X-Patchwork-Id: 10347045 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 3299B60365 for ; Tue, 17 Apr 2018 23:36:06 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 2BBB4205AB for ; Tue, 17 Apr 2018 23:36:06 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 2001F28334; Tue, 17 Apr 2018 23:36:06 +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=unavailable version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id C93C6205AB for ; Tue, 17 Apr 2018 23:36:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753012AbeDQXfw (ORCPT ); Tue, 17 Apr 2018 19:35:52 -0400 Received: from victor.provo.novell.com ([137.65.250.26]:41446 "EHLO prv3-mh.provo.novell.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752510AbeDQXfw (ORCPT ); Tue, 17 Apr 2018 19:35:52 -0400 Received: from apollon.suse.de.de (prv-ext-foundry1int.gns.novell.com [137.65.251.240]) by prv3-mh.provo.novell.com with ESMTP (TLS encrypted); Tue, 17 Apr 2018 17:35:38 -0600 From: Martin Wilck To: "Martin K. Petersen" Cc: linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org, Hannes Reinecke , James Bottomley , Xose Vazquez Perez , Bart Van Assche , Linus Torvalds , Ard Biesheuvel , Thomas Gleixner , Jonathan Corbet , Randy Dunlap Subject: [PATCH v3 1/6] ilog2: create truly constant version for sparse Date: Wed, 18 Apr 2018 01:35:06 +0200 Message-Id: <20180417233511.6573-2-mwilck@suse.com> X-Mailer: git-send-email 2.16.1 In-Reply-To: <20180417233511.6573-1-mwilck@suse.com> References: <20180417233511.6573-1-mwilck@suse.com> Sender: linux-scsi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-scsi@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Sparse emits errors about ilog2() in array indices because of the use of __ilog2_32() and __ilog2_64(), rightly so (https://www.spinics.net/lists/linux-sparse/msg03471.html). Create a const_ilog2() variant that works with sparse for this scenario. (Note: checkpatch.pl complains about missing parentheses, but that appears to be a false positive. I can get rid of the warning simply by inserting whitespace, making checkpatch "see" the whole macro). Signed-off-by: Martin Wilck --- include/linux/log2.h | 35 ++++++++++++++++++++++++----------- 1 file changed, 24 insertions(+), 11 deletions(-) diff --git a/include/linux/log2.h b/include/linux/log2.h index 41a1ae0..2af7f778 100644 --- a/include/linux/log2.h +++ b/include/linux/log2.h @@ -72,16 +72,13 @@ unsigned long __rounddown_pow_of_two(unsigned long n) } /** - * ilog2 - log base 2 of 32-bit or a 64-bit unsigned value + * const_ilog2 - log base 2 of 32-bit or a 64-bit constant unsigned value * @n: parameter * - * constant-capable log of base 2 calculation - * - this can be used to initialise global variables from constant data, hence - * the massive ternary operator construction - * - * selects the appropriately-sized optimised version depending on sizeof(n) + * Use this where sparse expects a true constant expression, e.g. for array + * indices. */ -#define ilog2(n) \ +#define const_ilog2(n) \ ( \ __builtin_constant_p(n) ? ( \ (n) < 2 ? 0 : \ @@ -147,10 +144,26 @@ unsigned long __rounddown_pow_of_two(unsigned long n) (n) & (1ULL << 4) ? 4 : \ (n) & (1ULL << 3) ? 3 : \ (n) & (1ULL << 2) ? 2 : \ - 1 ) : \ - (sizeof(n) <= 4) ? \ - __ilog2_u32(n) : \ - __ilog2_u64(n) \ + 1) : \ + -1) + +/** + * ilog2 - log base 2 of 32-bit or a 64-bit unsigned value + * @n: parameter + * + * constant-capable log of base 2 calculation + * - this can be used to initialise global variables from constant data, hence + * the massive ternary operator construction + * + * selects the appropriately-sized optimised version depending on sizeof(n) + */ +#define ilog2(n) \ +( \ + __builtin_constant_p(n) ? \ + const_ilog2(n) : \ + (sizeof(n) <= 4) ? \ + __ilog2_u32(n) : \ + __ilog2_u64(n) \ ) /**