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 X-Spam-Level: X-Spam-Status: No, score=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6C13CC43387 for ; Fri, 18 Jan 2019 16:27:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3FCC720883 for ; Fri, 18 Jan 2019 16:27:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728398AbfARQ1j (ORCPT ); Fri, 18 Jan 2019 11:27:39 -0500 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:33368 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727994AbfARQ1j (ORCPT ); Fri, 18 Jan 2019 11:27:39 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id B655BEBD; Fri, 18 Jan 2019 08:27:38 -0800 (PST) Received: from [10.1.196.69] (e112269-lin.cambridge.arm.com [10.1.196.69]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id C48DF3F557; Fri, 18 Jan 2019 08:27:36 -0800 (PST) Subject: Re: [PATCH 1/3] kconfig.h: abstract empty functions with STUB_UNLESS macro To: Andrew Murray , Masahiro Yamada , Arnd Bergmann , Kees Cook , Andrew Morton Cc: rjw@rjwysocki.net, Catalin Marinas , Will Deacon , linux-kernel@vger.kernel.org, Grant Likely , Dave P Martin , linux-arm-kernel@lists.infradead.org References: <1547827230-55132-1-git-send-email-andrew.murray@arm.com> <1547827230-55132-2-git-send-email-andrew.murray@arm.com> From: Steven Price Message-ID: <830dafb3-7e93-e655-464f-8cb821de8dd5@arm.com> Date: Fri, 18 Jan 2019 16:27:35 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0 MIME-Version: 1.0 In-Reply-To: <1547827230-55132-2-git-send-email-andrew.murray@arm.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-GB Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 18/01/2019 16:00, Andrew Murray wrote: > A common pattern found in header files is a function declaration dependent > on a CONFIG_ option being enabled, followed by an empty function for when > that option isn't enabled. This can often take up a lot of space and impact > code readability. > > Let's introduce the following STUB_UNLESS macro: > > STUB_UNLESS(CONFIG_FOO, [body], prototype) > > This evaluates to 'prototype' prepended with 'extern' if CONFIG_FOO is set > to 'y'. Otherwise it will evaluate to 'prototype' prepended with 'static > inline' followed by an empty function body. Where optional argument 'body' > then 'body' will be used as the function body, intended to allow for simple > return statements. > > Signed-off-by: Andrew Murray Seems like it should remove a lot of boilerplate code, so looks good to me. Reviewed-by: Steven Price > --- > include/linux/kconfig.h | 31 +++++++++++++++++++++++++++++++ > 1 file changed, 31 insertions(+) > > diff --git a/include/linux/kconfig.h b/include/linux/kconfig.h > index cc8fa10..216a27f 100644 > --- a/include/linux/kconfig.h > +++ b/include/linux/kconfig.h > @@ -12,6 +12,7 @@ > > #define __ARG_PLACEHOLDER_1 0, > #define __take_second_arg(__ignored, val, ...) val > +#define __take_fourth_arg(__ignored, __ignored2, __ignored3, val, ...) val > > /* > * The use of "&&" / "||" is limited in certain expressions. > @@ -70,4 +71,34 @@ > */ > #define IS_ENABLED(option) __or(IS_BUILTIN(option), IS_MODULE(option)) > > + > + > +/* > + * Allow for __stub to be overloaded by making the second argument optional > + */ > +#define __stub_overload(...) __take_fourth_arg(__VA_ARGS__, \ > + __stub_body, __stub_void)(__VA_ARGS__) > +#define __stub_body(option, body, ptype) __stub(option, body, ptype) > +#define __stub_void(option, ptype) __stub(option, , ptype) > + > +/* > + * Using the same trick as __defined we use the config option to conditionally > + * expand to an extern function declaration or a static stub function. > + */ > +#define __stub(option, body, ptype) ___stub( \ > + __ARG_PLACEHOLDER_##option, body, ptype) > +#define ___stub(arg1_or_junk, body, ptype) __take_second_arg( \ > + arg1_or_junk __extern_ptype(ptype), __static_ptype(body, ptype)) > +#define __static_ptype(body, ptype) static inline ptype { body; } > +#define __extern_ptype(ptype) extern ptype > + > +/* > + * STUB_UNLESS(CONFIG_FOO, [body], prototype) evaluates to 'prototype' prepended > + * with 'extern' if CONFIG_FOO is set to 'y'. Otherwise it will evaluate to > + * 'prototype' prepended with 'static inline' followed by an empty function > + * body. Where optional argument 'body' is present then 'body' will be used > + * as the function body, intended to allow for simple return statements. > + */ > +#define STUB_UNLESS(...) __stub_overload(__VA_ARGS__) > + > #endif /* __LINUX_KCONFIG_H */ >