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Wed, 09 Apr 2025 11:56:51 -0700 (PDT) Date: Thu, 10 Apr 2025 02:56:41 +0800 From: Kuan-Wei Chiu To: Yury Norov 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: brcm80211@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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: > > > > Refactor parity calculations to use the standard parity_odd() helper. > > > > This change eliminates redundant implementations. > > > > > > > > Co-developed-by: Yu-Chun Lin > > > > Signed-off-by: Yu-Chun Lin > > > > Signed-off-by: Kuan-Wei Chiu > > > > --- > > > > drivers/media/test-drivers/vivid/vivid-vbi-gen.c | 8 ++------ > > > > 1 file changed, 2 insertions(+), 6 deletions(-) > > > > > > > > diff --git a/drivers/media/test-drivers/vivid/vivid-vbi-gen.c b/drivers/media/test-drivers/vivid/vivid-vbi-gen.c > > > > index 70a4024d461e..5e1b7b1742e4 100644 > > > > --- a/drivers/media/test-drivers/vivid/vivid-vbi-gen.c > > > > +++ b/drivers/media/test-drivers/vivid/vivid-vbi-gen.c > > > > @@ -5,6 +5,7 @@ > > > > * Copyright 2014 Cisco Systems, Inc. and/or its affiliates. All rights reserved. > > > > */ > > > > > > > > +#include > > > > #include > > > > #include > > > > #include > > > > @@ -165,12 +166,7 @@ static const u8 vivid_cc_sequence2[30] = { > > > > > > > > static u8 calc_parity(u8 val) > > > > { > > > > - unsigned i; > > > > - unsigned tot = 0; > > > > - > > > > - for (i = 0; i < 7; i++) > > > > - tot += (val & (1 << i)) ? 1 : 0; > > > > - return val | ((tot & 1) ? 0 : 0x80); > > > > + return val | (parity_odd(val) ? 0 : 0x80); > > > > > > 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? Regards, Kuan-Wei > I think we need a comment from authors.