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 A0A29C76188 for ; Mon, 22 Jul 2019 15:05:23 +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 793172190F for ; Mon, 22 Jul 2019 15:05:23 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="F6kHiHkz" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 793172190F 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=B1Nhrr3pS75Kz92czjWKU/ztPdJojV+96wywlcuS4zY=; b=F6kHiHkzE+aNg3 MYVpeXpL3HVKSduKGCGt2dXsd0fhJsj2zmysUahUWBvA1BajP1gzdy4oDMxhXF3XIGdUODVAl0UmY qRquxd6UI2aL/aIkxAeDwqXZ/H7ZmLwv9US9PMRsBvGMsKHWPjBRy+oEzwpgnYMlnJkejPedoT1UN ldMN6gp4mZ8RWBKXHyUQyKPVhnBkK+e3y23q6xxzfk/6bDZhXQR5dRLa80iygyJfZct6EyPXAf16l uwx3Sw0oOFGjJofaZBY9CwhBs4gvgbI+ztpvGy75rcJUOYNLKhnZkXKJgoNBIUWEbFitLu+EPdJNS cXFdmNaXgG5GLX8jk9DA==; 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 1hpZsR-0000Pk-20; Mon, 22 Jul 2019 15:05:23 +0000 Received: from relay12.mail.gandi.net ([217.70.178.232]) by bombadil.infradead.org with esmtps (Exim 4.92 #3 (Red Hat Linux)) id 1hpZsN-0000PM-Mv for linux-arm-kernel@lists.infradead.org; Mon, 22 Jul 2019 15:05:21 +0000 Received: from aptenodytes (lfbn-1-17395-211.w86-250.abo.wanadoo.fr [86.250.200.211]) (Authenticated sender: paul.kocialkowski@bootlin.com) by relay12.mail.gandi.net (Postfix) with ESMTPSA id D960C20001D; Mon, 22 Jul 2019 15:05:16 +0000 (UTC) Date: Mon, 22 Jul 2019 17:05:16 +0200 From: Paul Kocialkowski To: Nishka Dasgupta Subject: Re: [PATCH v2] staging: media: sunxi: Add bool cast to value Message-ID: <20190722150516.GB31695@aptenodytes> References: <20190722060651.6538-1-nishkadg.linux@gmail.com> <20190722111225.GA2695@azazel.net> <20190722122438.GA1908@aptenodytes> <45555499-57f3-a315-6f84-f878c3aa0130@gmail.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <45555499-57f3-a315-6f84-f878c3aa0130@gmail.com> 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_080520_064837_501BA3D2 X-CRM114-Status: GOOD ( 34.76 ) 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, Jeremy Sowden , maxime.ripard@bootlin.com, gregkh@linuxfoundation.org, wens@csie.org, 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, 19:14, Nishka Dasgupta wrote: > On 22/07/19 5:54 PM, Paul Kocialkowski wrote: > > 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. > > It's not a problem per se. I'm just working on a cleanup project for which I > went through all of staging replacing single-line functions with what they > were calling. In some cases that makes it easier to figure out what a > particular function call does, since the called function actually does > something itself instead of just calling a different function? > This function was also flagged as one such potentially-removable function by > Coccinelle; but in order to do the same replacement that I'd done in other > staging drivers, I thought I would do something about the type mismatch > first, especially since find_format doesn't appear to be used anywhere else. > However, now I won't remove check_format and replace it with find_format as > I'd originally planned, since you've said that isn't necessary here. That > leaves the return type issue. Is that an issue reported by coccinelle? If so, could you provide details about it? > > So in the end, I think we should keep the !! and drop the (bool) cast if there's > > no particular warning about it. > > Should I send a version 3 that does this? Yes I think !! would work out fine either way. Apparently we don't need any explicit (bool) cast from a pointer anyway. Cheers, Paul > Thanking you, > Nishka > > > 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