From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.18]) (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 3D05D333443; Fri, 31 Oct 2025 09:54:38 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=192.198.163.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761904481; cv=none; b=JpVOiigNuUBhF8IUlhBDL0K/w+Bly4G0h6VeQ184pDKyGiiWh+u9oZQOS6RRNFLokuPi9+lTqx3iKI3ThawxPP8pj20ZPgIURVKeeZ3fe/R0JAsZSNZdUnSLQ84EllrS2/0A9bnJgrBW1j3cyQFTAGZGYdDqzt+ezoI3UEdPTJ0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761904481; c=relaxed/simple; bh=v6cA50shDse4b25yyBe2a2iAc/jDGF6aKsH7khX41VA=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=Ywm0b8KOu5SRTasFv14YJmKmoJp5m8UuwAy2AYlEwD9diyGeKGdGGVPHTJrIjaR1rtcXFy0Bfc+6swUUzwPpjqFEsduoYsJHtTIPLYU94CaSydeLLwV5RU3ITPc3xJp/kG0OaAWKbMJN5xV4bvErsMdT7B7pktOV7z9udRtwdAA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com; spf=pass smtp.mailfrom=linux.intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=Grj0I0sM; arc=none smtp.client-ip=192.198.163.18 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="Grj0I0sM" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1761904479; x=1793440479; h=date:from:to:cc:subject:message-id:references: mime-version:content-transfer-encoding:in-reply-to; bh=v6cA50shDse4b25yyBe2a2iAc/jDGF6aKsH7khX41VA=; b=Grj0I0sMvvIaOfT+6IDF8lVlw+SD/6Nl2TMpObur75Ks1K+IoOoXFJ5K iMpLoAF5+8dThjMaBif2Njg14A0ALeZDzLXVVkLWp/sgkTeyxlPRHszp5 YMO/qUMfqZsblXZ0eT8QAzBjZCtqZXgA/dHQYQwKrAY8ZJsTkDHvBJTzy Adw9/+DD2AOMpXNF2jlBEbwxxO6dJjmn85LKgBh50pSUubrWzcTwDE+K9 RGgiFVAMQn5nyWJuETVoeOUsR4rRtZYvDRYG6CrfqDKLx5VqpQqJ8S1PB WnLffxngH6PL+Fv0Du4KlETWZ+8VnYal9cd2wskBFBPYvbGxWFBBysDrZ A==; X-CSE-ConnectionGUID: BFArgXLQQguUVaupAAJtng== X-CSE-MsgGUID: 4QptMlgiS9ez/2NBA5rnxw== X-IronPort-AV: E=McAfee;i="6800,10657,11598"; a="63269853" X-IronPort-AV: E=Sophos;i="6.19,269,1754982000"; d="scan'208";a="63269853" Received: from fmviesa004.fm.intel.com ([10.60.135.144]) by fmvoesa112.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 31 Oct 2025 02:54:38 -0700 X-CSE-ConnectionGUID: rjQq+IrBQB6lTHj3dXT+ug== X-CSE-MsgGUID: VUcsmbyoRhqWiLd9scZVdA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.19,269,1754982000"; d="scan'208";a="191343912" Received: from mgoodin-mobl3.amr.corp.intel.com (HELO ashevche-desk.local) ([10.124.220.66]) by fmviesa004-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 31 Oct 2025 02:54:37 -0700 Received: from andy by ashevche-desk.local with local (Exim 4.98.2) (envelope-from ) id 1vElq3-00000004EGH-2YMt; Fri, 31 Oct 2025 11:54:31 +0200 Date: Fri, 31 Oct 2025 11:54:30 +0200 From: Andy Shevchenko To: David Laight Cc: Jonathan Cameron , linux-iio@vger.kernel.org, linux-kernel@vger.kernel.org, Jyoti Bhayana , Jonathan Cameron , David Lechner , Nuno =?iso-8859-1?Q?S=E1?= , Andy Shevchenko Subject: Re: [PATCH v1 1/1] iio: common: scmi_sensors: Replace const_ilog2() with ilog2() Message-ID: References: <20251031074500.3958667-1-andriy.shevchenko@linux.intel.com> <20251031094336.6f352b4f@pumpkin> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20251031094336.6f352b4f@pumpkin> Organization: Intel Finland Oy - BIC 0357606-4 - c/o Alberga Business Park, 6 krs, Bertel Jungin Aukio 5, 02600 Espoo On Fri, Oct 31, 2025 at 09:43:36AM +0000, David Laight wrote: > On Fri, 31 Oct 2025 08:45:00 +0100 > Andy Shevchenko wrote: ... > > tstamp_scale = sensor->sensor_info->tstamp_scale + > > - const_ilog2(NSEC_PER_SEC) / const_ilog2(10); > > + ilog2(NSEC_PER_SEC) / ilog2(10); > > Is that just a strange way of writing 9 ? Why? It's correct way of writing log¹⁰(NSEC_PER_SEC), the problem here is that "i" people do not think about :-) But we have intlog10(), I completely forgot about it. > Mathematically log2(x)/log2(10) is log10(x) - which would be 9. > The code does seem to be 'in luck' though. > NSEC_PER_SEC is 10^9 or 0x3b9aca00, so ilog2(NSEC_PER_SEC) is 29. > ilog2(10) is 3, and 29/3 is 9. > > Do the same for 10^10 and you get 11. That code looks like working by luck entirely, TBH. I just took the scope of the patch to start dropping const_ilog2() usages. -- With Best Regards, Andy Shevchenko