From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail.zytor.com (terminus.zytor.com [198.137.202.136]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2C97326A0E3; Thu, 13 Mar 2025 16:40:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.137.202.136 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741884007; cv=none; b=Ho5ccutEvWUvgehKhax/lAM1zDIUjz9c3dLl67HOMwbhsXUsxRVle+DnSU4xqdoPd7Qyu+Cpq0q8xz+dP+E7YT655C1rHAKsFbe/gImTP8Xecs8o31E7EPnZB+lE2m92//Uqoi71JBcTb4LfGWSBgzVcXliIbFO/BA0HKSQMhy8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741884007; c=relaxed/simple; bh=SaFIw7UgTgo6VXgT9++j90cTZypncDuuppnQ2OyQAgc=; h=Date:From:To:CC:Subject:In-Reply-To:References:Message-ID: MIME-Version:Content-Type; b=XwrVdY4yIgQLzHK/yci8I062cMN8L9HWzu3DZOXND7271pUjNd1O7agzs70OJWiMj/zpgKq58vOo+xFhQrKA6PdkUpUDKOrGGvWcxhYuFVf/nfdg8SSgDCGEAGYx7BCyrAN3hiv0+T5s4dq/SGu1JgAFQuQzRd+bpBo6sRndv9A= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=zytor.com; spf=pass smtp.mailfrom=zytor.com; dkim=pass (2048-bit key) header.d=zytor.com header.i=@zytor.com header.b=TAd1C3YU; arc=none smtp.client-ip=198.137.202.136 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=zytor.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=zytor.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=zytor.com header.i=@zytor.com header.b="TAd1C3YU" Received: from [127.0.0.1] ([76.133.66.138]) (authenticated bits=0) by mail.zytor.com (8.18.1/8.17.1) with ESMTPSA id 52DGaDdt3043136 (version=TLSv1.3 cipher=TLS_AES_128_GCM_SHA256 bits=128 verify=NO); Thu, 13 Mar 2025 09:36:13 -0700 DKIM-Filter: OpenDKIM Filter v2.11.0 mail.zytor.com 52DGaDdt3043136 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=zytor.com; s=2025021701; t=1741883777; bh=SaFIw7UgTgo6VXgT9++j90cTZypncDuuppnQ2OyQAgc=; h=Date:From:To:CC:Subject:In-Reply-To:References:From; b=TAd1C3YUnz1/m04KvWprrt25c59hDoEqP/HObNA2f0Bp4rp+Nb9PEJCNVXCw14Iiu q9Abs6+zDLtcCpZhdLC2JCZczf1qLTKYIQIMECs16cttjTwMK/9bSrYGHwOie5HClz /jcP+3xeKGlwUu0aUrtIeDMZT1ZuV3Y4f2fDZOzvoKjLs6qNj/nOaMpj13f7/0wDQR FTgUDEoLrytWaP9YL4WrPdL93XJwGvTwIwSUgo+vtkpLhxBsY0ibsq0svVoyhEkaAa CHnCGjith9nzaUr6Ath+5dakagWjzMXxHAYsyl+rXq8ZXPjgmXLSW6QTYUQphTnOMM hLTpcEZzd0lKw== Date: Thu, 13 Mar 2025 09:36:11 -0700 From: "H. Peter Anvin" To: Yury Norov CC: Jacob Keller , David Laight , Jiri Slaby , Ingo Molnar , Kuan-Wei Chiu , tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, jk@ozlabs.org, joel@jms.id.au, eajames@linux.ibm.com, andrzej.hajda@intel.com, neil.armstrong@linaro.org, rfoss@kernel.org, maarten.lankhorst@linux.intel.com, mripard@kernel.org, tzimmermann@suse.de, airlied@gmail.com, simona@ffwll.ch, dmitry.torokhov@gmail.com, mchehab@kernel.org, awalls@md.metrocast.net, hverkuil@xs4all.nl, miquel.raynal@bootlin.com, richard@nod.at, vigneshr@ti.com, louis.peens@corigine.com, andrew+netdev@lunn.ch, davem@davemloft.net, edumazet@google.com, pabeni@redhat.com, parthiban.veerasooran@microchip.com, arend.vanspriel@broadcom.com, johannes@sipsolutions.net, gregkh@linuxfoundation.org, akpm@linux-foundation.org, alistair@popple.id.au, linux@rasmusvillemoes.dk, Laurent.pinchart@ideasonboard.com, jonas@kwiboo.se, jernej.skrabec@gmail.com, kuba@kernel.org, linux-kernel@vger.kernel.org, linux-fsi@lists.ozlabs.org, dri-devel@lists.freedesktop.org, linux-input@vger.kernel.org, linux-media@vger.kernel.org, linux-mtd@lists.infradead.org, oss-drivers@corigine.com, netdev@vger.kernel.org, linux-wireless@vger.kernel.org, brcm80211@lists.linux.dev, brcm80211-dev-list.pdl@broadcom.com, linux-serial@vger.kernel.org, bpf@vger.kernel.org, jserv@ccns.ncku.edu.tw, Yu-Chun Lin Subject: Re: [PATCH v3 01/16] bitops: Change parity8() return type to bool User-Agent: K-9 Mail for Android In-Reply-To: References: <20250306162541.2633025-1-visitorckw@gmail.com> <20250306162541.2633025-2-visitorckw@gmail.com> <9d4b77da-18c5-4551-ae94-a2b9fe78489a@kernel.org> <20250307193643.28065d2d@pumpkin> <0F794C6F-32A9-4F34-9516-CEE24EA4BC49@zytor.com> Message-ID: <795281B1-9B8A-477F-8012-DECD14CB53E5@zytor.com> Precedence: bulk X-Mailing-List: linux-input@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable On March 13, 2025 9:24:38 AM PDT, Yury Norov wro= te: >On Wed, Mar 12, 2025 at 05:09:16PM -0700, H=2E Peter Anvin wrote: >> On March 12, 2025 4:56:31 PM PDT, Jacob Keller wrote: > >[=2E=2E=2E] > >> >This is really a question of whether you expect odd or even parity as >> >the "true" value=2E I think that would depend on context, and we may n= ot >> >reach a good consensus=2E >> > >> >I do agree that my brain would jump to "true is even, false is odd"=2E >> >However, I also agree returning the value as 0 for even and 1 for odd >> >kind of made sense before, and updating this to be a bool and then >> >requiring to switch all the callers is a bit obnoxious=2E=2E=2E >>=20 >> Odd =3D 1 =3D true is the only same definition=2E It is a bitwise XOR, = or sum mod 1=2E > >The x86 implementation will be "popcnt(val) & 1", right? So if we >choose to go with odd =3D=3D false, we'll have to add an extra negation= =2E >So because it's a purely conventional thing, let's just pick a simpler >one? > >Compiler's builtin parity() returns 1 for odd=2E > >Thanks, >Yury The x86 implementation, no, but there will be plenty of others having that= exact definition=2E