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 CA80DEB64D9 for ; Thu, 15 Jun 2023 09:37:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1343550AbjFOJhT (ORCPT ); Thu, 15 Jun 2023 05:37:19 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35720 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1343538AbjFOJgs (ORCPT ); Thu, 15 Jun 2023 05:36:48 -0400 Received: from relay4-d.mail.gandi.net (relay4-d.mail.gandi.net [217.70.183.196]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5AF252D56; Thu, 15 Jun 2023 02:35:52 -0700 (PDT) X-GND-Sasl: herve.codina@bootlin.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bootlin.com; s=gm1; t=1686821716; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=tdk5EMEjl4leBhCxd1dmifb+WUt3kNNJIw7zVJ9fvlo=; b=U5+zUg/GID9mrvw0SW2BWCeDcaoAOEp/x/CgseFY3XWUmPL01J0zoSq/8Va6ysMEa+X2Du hsEvgRUCZUQwpF1yVxAhgaTTUMR+d9IcLt1jL21WeuTm9jf4tWTyH7eYHu/FLMvFKbPPKS fniYUoDybjmi7sgME9oGudRDePLP9gewe837b+SdOxHNRdeorTL0Znk08Te/cM+54u0K/d KFsV1CNJkzDYqMAN1ADrLGFOKKKRCjCrHXaipr0XgxonwmxTEqP6Gv7S1cMFePSxtOSpmb XxpB4l2oL31c1jr60EZKbJpLknHS2918mQYjyMjVrVbJiQcvBF6OViTlV43w4A== X-GND-Sasl: herve.codina@bootlin.com X-GND-Sasl: herve.codina@bootlin.com X-GND-Sasl: herve.codina@bootlin.com X-GND-Sasl: herve.codina@bootlin.com X-GND-Sasl: herve.codina@bootlin.com X-GND-Sasl: herve.codina@bootlin.com X-GND-Sasl: herve.codina@bootlin.com X-GND-Sasl: herve.codina@bootlin.com X-GND-Sasl: herve.codina@bootlin.com X-GND-Sasl: herve.codina@bootlin.com X-GND-Sasl: herve.codina@bootlin.com X-GND-Sasl: herve.codina@bootlin.com X-GND-Sasl: herve.codina@bootlin.com X-GND-Sasl: herve.codina@bootlin.com X-GND-Sasl: herve.codina@bootlin.com X-GND-Sasl: herve.codina@bootlin.com Received: by mail.gandi.net (Postfix) with ESMTPSA id 0EC9EE0007; Thu, 15 Jun 2023 09:35:13 +0000 (UTC) Date: Thu, 15 Jun 2023 11:35:12 +0200 From: Herve Codina To: Andy Shevchenko Cc: Liam Girdwood , Mark Brown , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Jonathan Cameron , Lars-Peter Clausen , Jaroslav Kysela , Takashi Iwai , Kuninori Morimoto , alsa-devel@alsa-project.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-iio@vger.kernel.org, Christophe Leroy , Thomas Petazzoni Subject: Re: [PATCH v4 07/13] minmax: Introduce {min,max}_array() Message-ID: <20230615113512.07967677@bootlin.com> In-Reply-To: References: <20230614074904.29085-1-herve.codina@bootlin.com> <20230614074904.29085-8-herve.codina@bootlin.com> <20230614114214.1371485e@bootlin.com> <20230614223418.0d7e355d@bootlin.com> Organization: Bootlin X-Mailer: Claws Mail 4.1.1 (GTK 3.24.38; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org Hi Andy, On Thu, 15 Jun 2023 01:05:40 +0300 Andy Shevchenko wrote: > On Wed, Jun 14, 2023 at 11:34 PM Herve Codina wrote: > > On Wed, 14 Jun 2023 14:51:43 +0300 > > Andy Shevchenko wrote: > > > On Wed, Jun 14, 2023 at 12:42 PM Herve Codina wrote: > > > > On Wed, 14 Jun 2023 12:02:57 +0300 > > > > Andy Shevchenko wrote: > > > > > On Wed, Jun 14, 2023 at 10:49 AM Herve Codina wrote: > > ... > > > > > > > + typeof(__array[0] + 0) __element = __array[--__len]; \ > > > > > > > > > > Do we need the ' + 0' part? > > > > > > > > Yes. > > > > > > > > __array can be an array of const items and it is legitimate to get the > > > > minimum value from const items. > > > > > > > > typeof(__array[0]) keeps the const qualifier but we need to assign __element > > > > in the loop. > > > > One way to drop the const qualifier is to get the type from a rvalue computed > > > > from __array[0]. This rvalue has to have the exact same type with only the const > > > > dropped. > > > > '__array[0] + 0' was a perfect canditate. > > > > > > Seems like this also deserves a comment. But if the series is accepted > > > as is, it may be done as a follow up. > > > > > > > Finally not so simple ... > > I did some deeper tests and the macros need to be fixed. > > > > I hope this one (with comments added) is correct: > > --- 8 --- > > /* > > * Do not check the array parameter using __must_be_array(). > > * In the following legit use-case where the "array" passed is a simple pointer, > > * __must_be_array() will return a failure. > > * --- 8< --- > > * int *buff > > * ... > > * min = min_array(buff, nb_items); > > * --- 8< --- > > * > > * The first typeof(&(array)[0]) is needed in order to support arrays of both > > * 'int *buff' and 'int buf[N]' types. > > * > > * typeof(__array[0] + 0) used for __element is needed as the array can be an > > * array of const items. > > * In order to discard the const qualifier use an arithmetic operation (rvalue). > > > > * This arithmetic operation discard the const but also can lead to an integer > > discards > > > * promotion. For instance, a const s8 __array[0] lead to an int __element due > > leads > > > * to the promotion. > > * In this case, simple min() or max() operation fails (type mismatch). > > * Use min_t() or max_t() (op_t parameter) enforcing the type in order to avoid > > * the min() or max() failure. > > This part perhaps can be avoided. See below. > > > */ > > #define __minmax_array(op_t, array, len) ({ \ > > typeof(&(array)[0]) __array = (array); \ > > typeof(len) __len = (len); \ > > typeof(__array[0] + 0) __element = __array[--__len]; \ > > while (__len--) \ > > __element = op_t(typeof(__array[0]), __element, __array[__len]); \ > > But can't we instead have typeof(+(array[0])) in the definition of __element? > There are also other possible solutions: a) _Generic() with listed > const types to move them to non-const, and b) __auto_type (which is > supported by GCC 4.9 and clang, but not in the C11 standard). typeof(+(array[0])) keeps the promotion. __auto_type works with my gcc-12 but not with a gcc-5.5. Depending on the compiler version, it discards or keeps the const qualifier. For this reason I would prefer to not use it. Did the job using _Generic(). This lead to: --- 8< --- /* * Remove a const qualifier * _Generic(foo, type-name: association, ..., default: association) performs a * comparison against the foo type (not the qualified type). * Do not use the const keyword in the type-name as it will not match the * unqualified type of foo. */ #define __unconst_type_cases(type) \ unsigned type: (unsigned type)0, \ signed type: (signed type)0 #define __unconst_typeof(x) typeof( \ _Generic((x), \ char: (char)0, \ __unconst_type_cases(char), \ __unconst_type_cases(short), \ __unconst_type_cases(int), \ __unconst_type_cases(long), \ __unconst_type_cases(long long), \ default: (x))) /* * Do not check the array parameter using __must_be_array(). * In the following legit use-case where the "array" passed is a simple pointer, * __must_be_array() will return a failure. * --- 8< --- * int *buff * ... * min = min_array(buff, nb_items); * --- 8< --- * * The first typeof(&(array)[0]) is needed in order to support arrays of both * 'int *buff' and 'int buf[N]' types. * * The array can be an array of const items. * typeof() keeps the const qualifier. Use __unconst_typeof() in order to * discard the const qualifier for the __element variable. */ #define __minmax_array(op, array, len) ({ \ typeof(&(array)[0]) __array = (array); \ typeof(len) __len = (len); \ __unconst_typeof(__array[0]) __element = __array[--__len]; \ while (__len--) \ __element = op(__element, __array[__len]); \ __element; }) /** * min_array - return minimum of values present in an array * @array: array * @len: array length * * Note that @len must not be zero (empty array). */ #define min_array(array, len) __minmax_array(min, array, len) /** * max_array - return maximum of values present in an array * @array: array * @len: array length * * Note that @len must not be zero (empty array). */ #define max_array(array, len) __minmax_array(max, array, len) --- 8< --- Do you think it looks good ? For, the KUnit tests, I agree, it would be nice to have something. I need some more substantial work to implement and run the test in KUnit and the first task will be learning the KUnit test system. I will do that but out of this series. Thanks for your feedback and pointers, Hervé