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Thu, 10 Apr 2025 08:07:32 -0700 (PDT) Received: from localhost ([216.228.127.131]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-73bb1e51f1csm3501019b3a.145.2025.04.10.08.07.31 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 10 Apr 2025 08:07:31 -0700 (PDT) Date: Thu, 10 Apr 2025 11:07:29 -0400 From: Yury Norov To: Kuan-Wei Chiu Cc: 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, jirislaby@kernel.org, akpm@linux-foundation.org, jdelvare@suse.com, linux@roeck-us.net, alexandre.belloni@bootlin.com, pgaj@cadence.com, hpa@zytor.com, 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, Frank.Li@nxp.com, linux-hwmon@vger.kernel.org, linux-i3c@lists.infradead.org, david.laight.linux@gmail.com, andrew.cooper3@citrix.com, Yu-Chun Lin Subject: Re: [PATCH v4 02/13] media: media/test_drivers: Replace open-coded parity calculation with parity_odd() Message-ID: References: <20250409154356.423512-1-visitorckw@gmail.com> <20250409154356.423512-3-visitorckw@gmail.com> Precedence: bulk X-Mailing-List: netdev@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: On Thu, Apr 10, 2025 at 02:56:41AM +0800, Kuan-Wei Chiu wrote: > On Wed, Apr 09, 2025 at 02:41:03PM -0400, Yury Norov wrote: > > On Thu, Apr 10, 2025 at 02:23:09AM +0800, Kuan-Wei Chiu wrote: > > > On Wed, Apr 09, 2025 at 01:03:42PM -0400, Yury Norov wrote: > > > > On Wed, Apr 09, 2025 at 11:43:45PM +0800, Kuan-Wei Chiu wrote: > > > > So, if val == 0 than parity_odd(val) is also 0, and this can be > > > > simplified just to: > > > > return parity(val) ? 0 : 0x80; > > > > Or I miss something? > > > > > > > If val == 0x01, the return value of calc_parity() will remain 0x01. > > > If changed to return parity_odd(val) ? 0 : 0x80;, the return value will > > > be changed to 0x00. > > > > Sorry, I meant > > return val ? 0 : 0x80; > > > > This 'val | (parity_odd(val)' is only false when val == 0, right? > > When val != 0, compiler will return true immediately, not even calling > > parity(). > > > I'm still confused. > > Maybe you're interpreting the code as: > > (val | parity(val)) ? 0 : 0x80 > > But what we're trying to do is: > > val | (parity(val) ? 0 : 0x80) > > So, for example, if val == 0x06, the return value will be 0x86. > Only returning 0 or 0x80 seems wrong to me. > Or did I misunderstand something? I misread the whole construction. Sorry, you're right. Scratch this.