From patchwork Thu May 7 19:25:17 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Gustavo A. R. Silva" X-Patchwork-Id: 212092 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=-13.6 required=3.0 tests=DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING, 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 09BE6C38A2A for ; Thu, 7 May 2020 19:20:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D32B4208E4 for ; Thu, 7 May 2020 19:20:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588879252; bh=gdUcbJXVtT6YHaa/pRQ/6RwwYOCYa19E7kHEwdNGrpU=; h=Date:From:To:Cc:Subject:List-ID:From; b=ozWFsf5gZmGnhu/EHzd9ptGYQLnmUOOYZC2+wlhxMedaJ9ppk7pUDxIIyDe0WYrwz zbzeVVkS96tGUMOTBd36iwU4Obu0hc6Zz9/IflaOTWGggb7Cs3Gyy7MtqYUep8+Tmu DpkBSR2+dmI8TS3wAxy391XuUaBeDaDyhWFPzB6s= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728627AbgEGTUw (ORCPT ); Thu, 7 May 2020 15:20:52 -0400 Received: from mail.kernel.org ([198.145.29.99]:42412 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727837AbgEGTUw (ORCPT ); Thu, 7 May 2020 15:20:52 -0400 Received: from embeddedor (unknown [189.207.59.248]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id E0681208E4; Thu, 7 May 2020 19:20:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588879251; bh=gdUcbJXVtT6YHaa/pRQ/6RwwYOCYa19E7kHEwdNGrpU=; h=Date:From:To:Cc:Subject:From; b=FsM5D+H1Q0D/Ggqx8+VPzcsDC6kmAQhmprvGzjUpT5FE+WeaS/lkzXHF1GmuW/m4v JNmAF9UU71unvR3hIiR6a9sqwttWFIebrBMOqQDxQWevbmRCIDw+hRXHbPqs9c0Igk HyQdDDdvJtkGVPtBS5rBsuFcbAyFLAhnowjqUfGk= Date: Thu, 7 May 2020 14:25:17 -0500 From: "Gustavo A. R. Silva" To: Zhang Rui , Daniel Lezcano Cc: Amit Kucheria , linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] thermal: imx8mm: Replace zero-length array with flexible-array Message-ID: <20200507192517.GA16557@embeddedor> MIME-Version: 1.0 Content-Disposition: inline User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-pm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org The current codebase makes use of the zero-length array language extension to the C90 standard, but the preferred mechanism to declare variable-length types such as these ones is a flexible array member[1][2], introduced in C99: struct foo { int stuff; struct boo array[]; }; By making use of the mechanism above, we will get a compiler warning in case the flexible array does not occur last in the structure, which will help us prevent some kind of undefined behavior bugs from being inadvertently introduced[3] to the codebase from now on. Also, notice that, dynamic memory allocations won't be affected by this change: "Flexible array members have incomplete type, and so the sizeof operator may not be applied. As a quirk of the original implementation of zero-length arrays, sizeof evaluates to zero."[1] sizeof(flexible-array-member) triggers a warning because flexible array members have incomplete type[1]. There are some instances of code in which the sizeof operator is being incorrectly/erroneously applied to zero-length arrays and the result is zero. Such instances may be hiding some bugs. So, this work (flexible-array member conversions) will also help to get completely rid of those sorts of issues. This issue was found with the help of Coccinelle. [1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html [2] https://github.com/KSPP/linux/issues/21 [3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour") Signed-off-by: Gustavo A. R. Silva --- drivers/thermal/imx8mm_thermal.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/thermal/imx8mm_thermal.c b/drivers/thermal/imx8mm_thermal.c index 0d60f8d7894f..e6061e26d4ac 100644 --- a/drivers/thermal/imx8mm_thermal.c +++ b/drivers/thermal/imx8mm_thermal.c @@ -54,7 +54,7 @@ struct imx8mm_tmu { void __iomem *base; struct clk *clk; const struct thermal_soc_data *socdata; - struct tmu_sensor sensors[0]; + struct tmu_sensor sensors[]; }; static int imx8mm_tmu_get_temp(void *data, int *temp)