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[209.132.180.67]) by mx.google.com with ESMTP id t23si10027492eji.404.2019.11.27.10.08.28; Wed, 27 Nov 2019 10:08:52 -0800 (PST) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727033AbfK0SG0 (ORCPT + 99 others); Wed, 27 Nov 2019 13:06:26 -0500 Received: from foss.arm.com ([217.140.110.172]:51138 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726729AbfK0SG0 (ORCPT ); Wed, 27 Nov 2019 13:06:26 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 1924431B; Wed, 27 Nov 2019 10:06:25 -0800 (PST) Received: from [10.1.196.37] (e121345-lin.cambridge.arm.com [10.1.196.37]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 210853F6C4; Wed, 27 Nov 2019 10:06:20 -0800 (PST) Subject: Re: [PATCH v3 1/7] linux/log2.h: Add roundup/rounddown_pow_two64() family of functions To: Leon Romanovsky , Nicolas Saenz Julienne Cc: andrew.murray@arm.com, maz@kernel.org, linux-kernel@vger.kernel.org, Lorenzo Pieralisi , Hanjun Guo , Sudeep Holla , Tariq Toukan , Rob Herring , Frank Rowand , Shawn Lin , Heiko Stuebner , Christoph Hellwig , Marek Szyprowski , james.quinlan@broadcom.com, mbrugger@suse.com, f.fainelli@gmail.com, phil@raspberrypi.org, wahrenst@gmx.net, jeremy.linton@arm.com, linux-pci@vger.kernel.org, linux-rpi-kernel@lists.infradead.org, "Rafael J. Wysocki" , Len Brown , "David S. Miller" , Bjorn Helgaas , linux-acpi@vger.kernel.org, linux-arm-kernel@lists.infradead.org, netdev@vger.kernel.org, linux-rdma@vger.kernel.org, devicetree@vger.kernel.org, linux-rockchip@lists.infradead.org, iommu@lists.linux-foundation.org References: <20191126091946.7970-1-nsaenzjulienne@suse.de> <20191126091946.7970-2-nsaenzjulienne@suse.de> <20191126125137.GA10331@unreal> From: Robin Murphy Message-ID: <6e0b9079-9efd-2884-26d1-3db2d622079d@arm.com> Date: Wed, 27 Nov 2019 18:06:18 +0000 User-Agent: Mozilla/5.0 (X11; Linux aarch64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: <20191126125137.GA10331@unreal> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-GB Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 26/11/2019 12:51 pm, Leon Romanovsky wrote: > On Tue, Nov 26, 2019 at 10:19:39AM +0100, Nicolas Saenz Julienne wrote: >> Some users need to make sure their rounding function accepts and returns >> 64bit long variables regardless of the architecture. Sadly >> roundup/rounddown_pow_two() takes and returns unsigned longs. Create a >> new generic 64bit variant of the function and cleanup rougue custom >> implementations. > > Is it possible to create general roundup/rounddown_pow_two() which will > work correctly for any type of variables, instead of creating special > variant for every type? In fact, that is sort of the case already - roundup_pow_of_two() itself wraps ilog2() such that the constant case *is* type-independent. And since ilog2() handles non-constant values anyway, might it be reasonable to just take the strongly-typed __roundup_pow_of_two() helper out of the loop as below? Robin ----->8----- diff --git a/include/linux/log2.h b/include/linux/log2.h index 83a4a3ca3e8a..e825f8a6e8b5 100644 --- a/include/linux/log2.h +++ b/include/linux/log2.h @@ -172,11 +172,8 @@ unsigned long __rounddown_pow_of_two(unsigned long n) */ #define roundup_pow_of_two(n) \ ( \ - __builtin_constant_p(n) ? ( \ - (n == 1) ? 1 : \ - (1UL << (ilog2((n) - 1) + 1)) \ - ) : \ - __roundup_pow_of_two(n) \ + (__builtin_constant_p(n) && (n == 1)) ? \ + 1 : (1UL << (ilog2((n) - 1) + 1)) \ ) /**