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Fri, 04 Apr 2025 01:46:47 -0700 (PDT) Received: from visitorckw-System-Product-Name ([140.113.216.168]) by smtp.gmail.com with ESMTPSA id 41be03b00d2f7-af9bc34ec32sm2448099a12.35.2025.04.04.01.46.38 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 04 Apr 2025 01:46:46 -0700 (PDT) Date: Fri, 4 Apr 2025 16:46:37 +0800 From: Kuan-Wei Chiu To: Jeremy Kerr Cc: Yury Norov , "H. Peter Anvin" , David Laight , Andrew Cooper , Laurent.pinchart@ideasonboard.com, airlied@gmail.com, akpm@linux-foundation.org, alistair@popple.id.au, andrew+netdev@lunn.ch, andrzej.hajda@intel.com, arend.vanspriel@broadcom.com, awalls@md.metrocast.net, bp@alien8.de, bpf@vger.kernel.org, brcm80211-dev-list.pdl@broadcom.com, brcm80211@lists.linux.dev, dave.hansen@linux.intel.com, davem@davemloft.net, dmitry.torokhov@gmail.com, dri-devel@lists.freedesktop.org, eajames@linux.ibm.com, edumazet@google.com, eleanor15x@gmail.com, gregkh@linuxfoundation.org, hverkuil@xs4all.nl, jernej.skrabec@gmail.com, jirislaby@kernel.org, joel@jms.id.au, johannes@sipsolutions.net, jonas@kwiboo.se, jserv@ccns.ncku.edu.tw, kuba@kernel.org, linux-fsi@lists.ozlabs.org, linux-input@vger.kernel.org, linux-kernel@vger.kernel.org, linux-media@vger.kernel.org, linux-mtd@lists.infradead.org, linux-serial@vger.kernel.org, linux-wireless@vger.kernel.org, linux@rasmusvillemoes.dk, louis.peens@corigine.com, maarten.lankhorst@linux.intel.com, mchehab@kernel.org, mingo@redhat.com, miquel.raynal@bootlin.com, mripard@kernel.org, neil.armstrong@linaro.org, netdev@vger.kernel.org, oss-drivers@corigine.com, pabeni@redhat.com, parthiban.veerasooran@microchip.com, rfoss@kernel.org, richard@nod.at, simona@ffwll.ch, tglx@linutronix.de, tzimmermann@suse.de, vigneshr@ti.com, x86@kernel.org Subject: Re: [PATCH v3 00/16] Introduce and use generic parity16/32/64 helper Message-ID: References: <80771542-476C-493E-858A-D2AF6A355CC1@zytor.com> <3ebd280e6697790da55f88a5e9e87b4cab407253.camel@ozlabs.org> 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: <3ebd280e6697790da55f88a5e9e87b4cab407253.camel@ozlabs.org> Hi Jeremy, On Fri, Apr 04, 2025 at 10:51:55AM +0800, Jeremy Kerr wrote: > Hi Yuri & Kuan-Wei: > > > Thank you for sharing your opinion on this fixed parity(). Your > > arguments may or may not be important, depending on what existing > > users actually need. Unfortunately, Kuan-Wei didn't collect > > performance numbers and opinions from those proposed users. > > For the fsi-i2c side: this isn't a performance-critical path, and any > reasonable common approach would likely perform better that the current > per-bit implementation. > > Our common targets for this driver would be arm and powerpc64le. In case > it's useful as a reference, using the kernel compilers I have to hand, a > __builtin_parity() is a library call on the former, and a two-instruction > sequence for the latter. > Thanks for your feedback. IIUC, from the fsi-i2c perspective, parity efficiency isn't a major concern, but you still prefer optimizing with methods like __builtin_parity(). I'm just unsure if this aligns with Yury's point about needing "evidence that performance and/or code generation is important here." Regards, Kuna-Wei