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=-8.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 16599C76188 for ; Mon, 22 Jul 2019 12:24:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id EA4A420665 for ; Mon, 22 Jul 2019 12:24:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727594AbfGVMYn (ORCPT ); Mon, 22 Jul 2019 08:24:43 -0400 Received: from relay11.mail.gandi.net ([217.70.178.231]:50447 "EHLO relay11.mail.gandi.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727040AbfGVMYn (ORCPT ); Mon, 22 Jul 2019 08:24:43 -0400 Received: from aptenodytes (lfbn-1-17395-211.w86-250.abo.wanadoo.fr [86.250.200.211]) (Authenticated sender: paul.kocialkowski@bootlin.com) by relay11.mail.gandi.net (Postfix) with ESMTPSA id C6615100005; Mon, 22 Jul 2019 12:24:38 +0000 (UTC) Date: Mon, 22 Jul 2019 14:24:38 +0200 From: Paul Kocialkowski To: Jeremy Sowden Cc: Nishka Dasgupta , maxime.ripard@bootlin.com, mchehab@kernel.org, gregkh@linuxfoundation.org, wens@csie.org, linux-media@vger.kernel.org, devel@driverdev.osuosl.org, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH v2] staging: media: sunxi: Add bool cast to value Message-ID: <20190722122438.GA1908@aptenodytes> References: <20190722060651.6538-1-nishkadg.linux@gmail.com> <20190722111225.GA2695@azazel.net> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20190722111225.GA2695@azazel.net> User-Agent: Mutt/1.12.1 (2019-06-15) Sender: linux-media-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org Hi, On Mon 22 Jul 19, 12:12, Jeremy Sowden wrote: > On 2019-07-22, at 11:36:51 +0530, Nishka Dasgupta wrote: > > Typecast as bool the return value of cedrus_find_format in > > cedrus_check_format as the return value of cedrus_check_format is > > always treated like a boolean value. > > > > Signed-off-by: Nishka Dasgupta > > --- > > Changes in v2: > > - Add !! to the returned pointer to ensure that the return value is > > always either true or false, and never a non-zero value other than > > true. > > > > drivers/staging/media/sunxi/cedrus/cedrus_video.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/drivers/staging/media/sunxi/cedrus/cedrus_video.c b/drivers/staging/media/sunxi/cedrus/cedrus_video.c > > index e2b530b1a956..b731745f21f8 100644 > > --- a/drivers/staging/media/sunxi/cedrus/cedrus_video.c > > +++ b/drivers/staging/media/sunxi/cedrus/cedrus_video.c > > @@ -86,7 +86,7 @@ static struct cedrus_format *cedrus_find_format(u32 pixelformat, u32 directions, > > static bool cedrus_check_format(u32 pixelformat, u32 directions, > > unsigned int capabilities) > > { > > - return cedrus_find_format(pixelformat, directions, capabilities); > > + return !!(bool)cedrus_find_format(pixelformat, directions, capabilities); > > } > > I think the original was fine. The return value of cedrus_find_format > will be automatically converted to bool before being returned from > cedrus_check_format since that is the return-type of the function, and > the result of converting any non-zero value to bool is 1. Okay I was a bit unsure about that and wanted to play it on the safe side without really looking it up, but that gave me the occasion to verify. >From what I could find (from my GNU system's /usr/include/unistring/stdbool.h): Limitations of this substitute, when used in a C89 environment: - In C99, casts and automatic conversions to '_Bool' or 'bool' are performed in such a way that every nonzero value gets converted to 'true', and zero gets converted to 'false'. This doesn't work with this substitute. With this substitute, only the values 0 and 1 give the expected result when converted to _Bool' or 'bool'. So since the kernel is built for C89 (unless I'm mistaken), I don't think the compiler provides any guarantee about bool values being converted to 1 when they are non-zero. As a result, I think it's best to be careful. However, I'm not sure I really see what cocinelle was unhappy about. You mentionned single-line functions, but I don't see how that can be a problem. So in the end, I think we should keep the !! and drop the (bool) cast if there's no particular warning about it. What do you think? Cheers, Paul > > static void cedrus_prepare_format(struct v4l2_pix_format *pix_fmt) > > -- > > 2.19.1 -- Paul Kocialkowski, Bootlin Embedded Linux and kernel engineering https://bootlin.com From mboxrd@z Thu Jan 1 00:00:00 1970 From: paul.kocialkowski@bootlin.com (Paul Kocialkowski) Date: Mon, 22 Jul 2019 14:24:38 +0200 Subject: [PATCH v2] staging: media: sunxi: Add bool cast to value In-Reply-To: <20190722111225.GA2695@azazel.net> References: <20190722060651.6538-1-nishkadg.linux@gmail.com> <20190722111225.GA2695@azazel.net> Message-ID: <20190722122438.GA1908@aptenodytes> List-Id: Linux Driver Project Developer List Hi, On Mon 22 Jul 19, 12:12, Jeremy Sowden wrote: > On 2019-07-22,@11:36:51 +0530, Nishka Dasgupta wrote: > > Typecast as bool the return value of cedrus_find_format in > > cedrus_check_format as the return value of cedrus_check_format is > > always treated like a boolean value. > > > > Signed-off-by: Nishka Dasgupta > > --- > > Changes in v2: > > - Add !! to the returned pointer to ensure that the return value is > > always either true or false, and never a non-zero value other than > > true. > > > > drivers/staging/media/sunxi/cedrus/cedrus_video.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/drivers/staging/media/sunxi/cedrus/cedrus_video.c b/drivers/staging/media/sunxi/cedrus/cedrus_video.c > > index e2b530b1a956..b731745f21f8 100644 > > --- a/drivers/staging/media/sunxi/cedrus/cedrus_video.c > > +++ b/drivers/staging/media/sunxi/cedrus/cedrus_video.c > > @@ -86,7 +86,7 @@ static struct cedrus_format *cedrus_find_format(u32 pixelformat, u32 directions, > > static bool cedrus_check_format(u32 pixelformat, u32 directions, > > unsigned int capabilities) > > { > > - return cedrus_find_format(pixelformat, directions, capabilities); > > + return !!(bool)cedrus_find_format(pixelformat, directions, capabilities); > > } > > I think the original was fine. The return value of cedrus_find_format > will be automatically converted to bool before being returned from > cedrus_check_format since that is the return-type of the function, and > the result of converting any non-zero value to bool is 1. Okay I was a bit unsure about that and wanted to play it on the safe side without really looking it up, but that gave me the occasion to verify. >>From what I could find (from my GNU system's /usr/include/unistring/stdbool.h): Limitations of this substitute, when used in a C89 environment: - In C99, casts and automatic conversions to '_Bool' or 'bool' are performed in such a way that every nonzero value gets converted to 'true', and zero gets converted to 'false'. This doesn't work with this substitute. With this substitute, only the values 0 and 1 give the expected result when converted to _Bool' or 'bool'. So since the kernel is built for C89 (unless I'm mistaken), I don't think the compiler provides any guarantee about bool values being converted to 1 when they are non-zero. As a result, I think it's best to be careful. However, I'm not sure I really see what cocinelle was unhappy about. You mentionned single-line functions, but I don't see how that can be a problem. So in the end, I think we should keep the !! and drop the (bool) cast if there's no particular warning about it. What do you think? Cheers, Paul > > static void cedrus_prepare_format(struct v4l2_pix_format *pix_fmt) > > -- > > 2.19.1 -- Paul Kocialkowski, Bootlin Embedded Linux and kernel engineering https://bootlin.com 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=-8.3 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable 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 676AEC76190 for ; Mon, 22 Jul 2019 12:24:57 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 3911E218EA for ; Mon, 22 Jul 2019 12:24:57 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="hY3Ir56C" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3911E218EA Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=bootlin.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=Yd/1apRjdGV9IzoeSWjxahSRnioU5iPid+/aV44t7OM=; b=hY3Ir56CSV6P0i dptUQaiT4Lix2jzIKmKGabFuTpdoTKcnzY03UACsCX3PL8PDuootAu2VGce7wBmiCCIbFvRm3STLy /8CkV0qq58Fbel9JcvKWE9O+VeO7QrSD5DlRDY4o7Va/KLKZqKIzIyVh2QYffDXWBeOW2xufb4Gd0 qvPjmCjGFKRYQGFQP3DkSM/CzmJA0pjV07P/lwKxgVH4pkCEai7Js7vGxlk0N/JRVxduSEcg/SqQD QyFbqbCwjEyhI99q2FV5pSG7NFkSEUAWHkCMPPYRPa7rNC1uLyi8RVUdzS7i8eP4NVANP8f0xZxUf PfSXFwMLVwEuhXjtJzzQ==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92 #3 (Red Hat Linux)) id 1hpXNA-0006ws-Qu; Mon, 22 Jul 2019 12:24:56 +0000 Received: from relay11.mail.gandi.net ([217.70.178.231]) by bombadil.infradead.org with esmtps (Exim 4.92 #3 (Red Hat Linux)) id 1hpXN5-0006vV-Vd for linux-arm-kernel@lists.infradead.org; Mon, 22 Jul 2019 12:24:54 +0000 Received: from aptenodytes (lfbn-1-17395-211.w86-250.abo.wanadoo.fr [86.250.200.211]) (Authenticated sender: paul.kocialkowski@bootlin.com) by relay11.mail.gandi.net (Postfix) with ESMTPSA id C6615100005; Mon, 22 Jul 2019 12:24:38 +0000 (UTC) Date: Mon, 22 Jul 2019 14:24:38 +0200 From: Paul Kocialkowski To: Jeremy Sowden Subject: Re: [PATCH v2] staging: media: sunxi: Add bool cast to value Message-ID: <20190722122438.GA1908@aptenodytes> References: <20190722060651.6538-1-nishkadg.linux@gmail.com> <20190722111225.GA2695@azazel.net> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20190722111225.GA2695@azazel.net> User-Agent: Mutt/1.12.1 (2019-06-15) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190722_052452_172007_A059904D X-CRM114-Status: GOOD ( 22.06 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: devel@driverdev.osuosl.org, maxime.ripard@bootlin.com, gregkh@linuxfoundation.org, wens@csie.org, Nishka Dasgupta , mchehab@kernel.org, linux-arm-kernel@lists.infradead.org, linux-media@vger.kernel.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi, On Mon 22 Jul 19, 12:12, Jeremy Sowden wrote: > On 2019-07-22, at 11:36:51 +0530, Nishka Dasgupta wrote: > > Typecast as bool the return value of cedrus_find_format in > > cedrus_check_format as the return value of cedrus_check_format is > > always treated like a boolean value. > > > > Signed-off-by: Nishka Dasgupta > > --- > > Changes in v2: > > - Add !! to the returned pointer to ensure that the return value is > > always either true or false, and never a non-zero value other than > > true. > > > > drivers/staging/media/sunxi/cedrus/cedrus_video.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/drivers/staging/media/sunxi/cedrus/cedrus_video.c b/drivers/staging/media/sunxi/cedrus/cedrus_video.c > > index e2b530b1a956..b731745f21f8 100644 > > --- a/drivers/staging/media/sunxi/cedrus/cedrus_video.c > > +++ b/drivers/staging/media/sunxi/cedrus/cedrus_video.c > > @@ -86,7 +86,7 @@ static struct cedrus_format *cedrus_find_format(u32 pixelformat, u32 directions, > > static bool cedrus_check_format(u32 pixelformat, u32 directions, > > unsigned int capabilities) > > { > > - return cedrus_find_format(pixelformat, directions, capabilities); > > + return !!(bool)cedrus_find_format(pixelformat, directions, capabilities); > > } > > I think the original was fine. The return value of cedrus_find_format > will be automatically converted to bool before being returned from > cedrus_check_format since that is the return-type of the function, and > the result of converting any non-zero value to bool is 1. Okay I was a bit unsure about that and wanted to play it on the safe side without really looking it up, but that gave me the occasion to verify. >From what I could find (from my GNU system's /usr/include/unistring/stdbool.h): Limitations of this substitute, when used in a C89 environment: - In C99, casts and automatic conversions to '_Bool' or 'bool' are performed in such a way that every nonzero value gets converted to 'true', and zero gets converted to 'false'. This doesn't work with this substitute. With this substitute, only the values 0 and 1 give the expected result when converted to _Bool' or 'bool'. So since the kernel is built for C89 (unless I'm mistaken), I don't think the compiler provides any guarantee about bool values being converted to 1 when they are non-zero. As a result, I think it's best to be careful. However, I'm not sure I really see what cocinelle was unhappy about. You mentionned single-line functions, but I don't see how that can be a problem. So in the end, I think we should keep the !! and drop the (bool) cast if there's no particular warning about it. What do you think? Cheers, Paul > > static void cedrus_prepare_format(struct v4l2_pix_format *pix_fmt) > > -- > > 2.19.1 -- Paul Kocialkowski, Bootlin Embedded Linux and kernel engineering https://bootlin.com _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel