From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 4C21B1DF963; Mon, 24 Feb 2025 07:09:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740380997; cv=none; b=OTISCSAYBlcavBnIiqFAE1BBitL0hfotO8UxlUC0LOOTXq/m5kKxd5aSmaXjOSkl9sabv3jjRsd4B6cy82EQhmdHfFjzKSESMHsy8U52jZX2gmNKwTkLYDMh/XV1jaXlfvndY/g5Blo3vyw298kNGxtUzPfScLgtWgGkI/bncHY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740380997; c=relaxed/simple; bh=fkASXmTFBo3Vl/klcz2dL1xKweKD4YSi26z5tvTK/J4=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=vAFy4pOywzmnZCemICpHZIglVjKx/rcOjhnxAxq6d4JXNC4L5qYuhyVuZkmsXN0EuePfx7TBPGUuEI3W/Ox6o1KLlOUajXP8K9v0qxfo+HoovaviHZDnz9tTpiXalcOpWABSa9EghVfvb81iTRxEtaWe5VjggFPTqLcJwVu3PIo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=FFicEGbS; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="FFicEGbS" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 03944C4CED6; Mon, 24 Feb 2025 07:09:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1740380996; bh=fkASXmTFBo3Vl/klcz2dL1xKweKD4YSi26z5tvTK/J4=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=FFicEGbSi56eSM0TXBdNGJZR6fyVj+36fd8Gmxf4LjhTEySCctA9GqzxpCjUDpfSL 08Dx0KXfpmwPYGDHCDryGnRcCWDrE/aZF5kNI8zw1N4i9gU8E2AhbeTcQjT1TJqMNA 7ykt4xwW+uATbSuqvLn2zrI+hZSeC+1/RAttYQTvRzkwbCUVR++Xv8GzLBF7nbG80w JZblYfa/c4q/ZdVDmLtzW/ix78wFgASzmTk9H/f+Z51ByZZhEvlKT9bGXwtBj1WjDq Pww4k4uxAbknRXPdJkgCEAFJpaVEcCST592dPPd9SJ3YLnKwsyg2B+yILZVl8zJg7A 8hY8zjq85rorg== Message-ID: Date: Mon, 24 Feb 2025 08:09:43 +0100 Precedence: bulk X-Mailing-List: linux-input@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 02/17] bitops: Add generic parity calculation for u64 To: 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, yury.norov@gmail.com, akpm@linux-foundation.org Cc: 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, Yu-Chun Lin References: <20250223164217.2139331-1-visitorckw@gmail.com> <20250223164217.2139331-3-visitorckw@gmail.com> Content-Language: en-US From: Jiri Slaby Autocrypt: addr=jirislaby@kernel.org; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 23. 02. 25, 17:42, Kuan-Wei Chiu wrote: > Several parts of the kernel open-code parity calculations using > different methods. Add a generic parity64() helper implemented with the > same efficient approach as parity8(). > > Co-developed-by: Yu-Chun Lin > Signed-off-by: Yu-Chun Lin > Signed-off-by: Kuan-Wei Chiu > --- > include/linux/bitops.h | 22 ++++++++++++++++++++++ > 1 file changed, 22 insertions(+) > > diff --git a/include/linux/bitops.h b/include/linux/bitops.h > index fb13dedad7aa..67677057f5e2 100644 > --- a/include/linux/bitops.h > +++ b/include/linux/bitops.h > @@ -281,6 +281,28 @@ static inline int parity32(u32 val) > return (0x6996 >> (val & 0xf)) & 1; > } > > +/** > + * parity64 - get the parity of an u64 value > + * @value: the value to be examined > + * > + * Determine the parity of the u64 argument. > + * > + * Returns: > + * 0 for even parity, 1 for odd parity > + */ > +static inline int parity64(u64 val) > +{ > + /* > + * One explanation of this algorithm: > + * https://funloop.org/codex/problem/parity/README.html > + */ > + val ^= val >> 32; Do we need all these implementations? Can't we simply use parity64() for any 8, 16 and 32-bit values too? I.e. have one parity(). > + val ^= val >> 16; > + val ^= val >> 8; > + val ^= val >> 4; > + return (0x6996 >> (val & 0xf)) & 1; > +} > + > /** > * __ffs64 - find first set bit in a 64 bit word > * @word: The 64 bit word -- js suse labs