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Peter Anvin" 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 Message-ID: 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> 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=us-ascii Content-Disposition: inline In-Reply-To: <0F794C6F-32A9-4F34-9516-CEE24EA4BC49@zytor.com> On Wed, Mar 12, 2025 at 05:09:16PM -0700, H. Peter Anvin wrote: > On March 12, 2025 4:56:31 PM PDT, Jacob Keller wrote: [...] > >This is really a question of whether you expect odd or even parity as > >the "true" value. I think that would depend on context, and we may not > >reach a good consensus. > > > >I do agree that my brain would jump to "true is even, false is odd". > >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... > > Odd = 1 = true is the only same definition. It is a bitwise XOR, or sum mod 1. The x86 implementation will be "popcnt(val) & 1", right? So if we choose to go with odd == false, we'll have to add an extra negation. So because it's a purely conventional thing, let's just pick a simpler one? Compiler's builtin parity() returns 1 for odd. Thanks, Yury