From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 65320E810DB for ; Wed, 27 Sep 2023 12:17:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231547AbjI0MRT (ORCPT ); Wed, 27 Sep 2023 08:17:19 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55282 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231608AbjI0MRQ (ORCPT ); Wed, 27 Sep 2023 08:17:16 -0400 Received: from mgamail.intel.com (mgamail.intel.com [192.55.52.115]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 615AE19A; Wed, 27 Sep 2023 05:17:14 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1695817034; x=1727353034; h=date:from:to:cc:subject:message-id:references: mime-version:in-reply-to; bh=QmuETALrgMPjUAn12YFgIQeDTtWH91/gn8tjyGX6uwM=; b=diFgkx02bfYFxlgNRQjJY0PysoNjOPtbpssq4JmVVE0mFlwyGn/psfVX qpArlH28IBZ7sxgZCJ+bP/Ap11phykhvRn4RG3C3HMI3HF+kA7kiLlvOK r0clrjJLh5UP4WcHONSZ3XgWpy1YtroJ3JcKxa7b1GaWQioQp8RLufyKB ZSKzHEdpxdu/R5nYZDrGgwH7nS28Nw15HoD3bUa41L61yebOCGg+xTbQD 8VmiCNK4Ft06dLEZTKV176Xn5qIrpGS/PVp3EUnUWY8NlaQfbxgYy/8Mr ROCPCUuHTZBfOquzv94Ifch3U932C4+lNjDx/Oc7MNshT6wQr1DzTFJr9 A==; X-IronPort-AV: E=McAfee;i="6600,9927,10845"; a="381710844" X-IronPort-AV: E=Sophos;i="6.03,181,1694761200"; d="scan'208";a="381710844" Received: from orsmga008.jf.intel.com ([10.7.209.65]) by fmsmga103.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 27 Sep 2023 05:17:13 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10845"; a="778518582" X-IronPort-AV: E=Sophos;i="6.03,181,1694761200"; d="scan'208";a="778518582" Received: from smile.fi.intel.com ([10.237.72.54]) by orsmga008.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 27 Sep 2023 05:17:09 -0700 Received: from andy by smile.fi.intel.com with local (Exim 4.97-RC0) (envelope-from ) id 1qlTTW-00000000scN-2fgC; Wed, 27 Sep 2023 15:17:06 +0300 Date: Wed, 27 Sep 2023 15:17:06 +0300 From: Andy Shevchenko To: Kent Gibson Cc: Linus Walleij , Bartosz Golaszewski , Yury Norov , linux-gpio@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Shubhrajyoti Datta , Srinivas Neeli , Michal Simek , Bartosz Golaszewski , Rasmus Villemoes , Marek =?iso-8859-1?Q?Beh=FAn?= Subject: Re: [PATCH v1 5/5] gpiolib: cdev: Utilize more bitmap APIs Message-ID: References: <20230926052007.3917389-1-andriy.shevchenko@linux.intel.com> <20230926052007.3917389-6-andriy.shevchenko@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Sep 27, 2023 at 09:32:11AM +0800, Kent Gibson wrote: > On Tue, Sep 26, 2023 at 08:20:07AM +0300, Andy Shevchenko wrote: > > Currently we have a few bitmap calls that are open coded in the library > > module. Let's convert them to use generic bitmap APIs instead. > > Firstly, I didn't consider using the bitmap module here as, in my mind at > least, that is intended for bitmaps wider than 64 bits, or with variable > width. In this case the bitmap is fixed at 64 bits, so bitops seemed more > appropriate. > > And I would argue that they aren't "open coded" - they are parallelized > to reduce the number of passes over the bitmap. > This change serialises them, e.g. the get used to require 2 passes over > the bitmap, it now requires 3 or 4. The set used to require 1 and now > requires 2. > And there are additional copies that the original doesn't require. > So your change looks less efficient to me - unless there is direct > hardware support for bitmap ops?? > > Wrt the argument that the serialized form is clearer and more > maintainable, optimised code is frequently more cryptic - as noted in > bitmap.c itself, and this code has remained unchanged since it was merged > 3 years ago, so the only maintenance it has required is to be more > maintainable?? Ok then. > > Your patch is functionally equivalent and pass my uAPI tests, so > > Tested-by: Kent Gibson Thanks for testing! > but my preference is to leave it as is. As Yury mentioned we need to look at bitmap APIs and make them possible to have a compile-time optimizations. With that in mind, I would prefer bitmap APIs over open-coded stuff which is hardly to be understood (yes, I still point out that it takes a few hours to me, maybe because I'm stupid enough, to get what's the heck is going one there, esp. for the == 1 case). Yet, it opens a way to scale this in case we might have v3 ABI that let's say allows to work with 512 GPIOs at a time. With your code it will be much harder to achieve and see what you wrote about maintenance (in that case). -- With Best Regards, Andy Shevchenko