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=-5.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_2 autolearn=no 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 00BDFC4727C for ; Thu, 1 Oct 2020 08:12:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B763D208B8 for ; Thu, 1 Oct 2020 08:12:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730862AbgJAIMM convert rfc822-to-8bit (ORCPT ); Thu, 1 Oct 2020 04:12:12 -0400 Received: from relay1-d.mail.gandi.net ([217.70.183.193]:56687 "EHLO relay1-d.mail.gandi.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725878AbgJAIMM (ORCPT ); Thu, 1 Oct 2020 04:12:12 -0400 X-Originating-IP: 91.224.148.103 Received: from xps13 (unknown [91.224.148.103]) (Authenticated sender: miquel.raynal@bootlin.com) by relay1-d.mail.gandi.net (Postfix) with ESMTPSA id ECF2124000D; Thu, 1 Oct 2020 08:12:07 +0000 (UTC) Date: Thu, 1 Oct 2020 10:12:06 +0200 From: Miquel Raynal To: Jann Horn Cc: "Gustavo A. R. Silva" , Stefan Agner , Lucas Stach , Richard Weinberger , Vignesh Raghavendra , Thierry Reding , Jonathan Hunter , linux-mtd@lists.infradead.org, linux-tegra@vger.kernel.org, kernel list , linux-hardening@vger.kernel.org Subject: Re: [PATCH][next] mtd: rawnand: Replace one-element array with flexible-array member Message-ID: <20201001101206.6e4beea7@xps13> In-Reply-To: References: <20200930210824.GA12277@embeddedor> <20200930213634.GA12855@embeddedor> Organization: Bootlin X-Mailer: Claws Mail 3.17.4 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Jann, Jann Horn wrote on Thu, 1 Oct 2020 00:32:24 +0200: > On Wed, Sep 30, 2020 at 11:30 PM Gustavo A. R. Silva > wrote: > > On Wed, Sep 30, 2020 at 11:10:43PM +0200, Jann Horn wrote: > > > On Wed, Sep 30, 2020 at 11:02 PM Gustavo A. R. Silva > > > wrote: > > > > There is a regular need in the kernel to provide a way to declare having > > > > a dynamically sized set of trailing elements in a structure. Kernel code > > > > should always use “flexible array members”[1] for these cases. The older > > > > style of one-element or zero-length arrays should no longer be used[2]. > > > > > > But this is not such a case, right? Isn't this a true fixed-size > > > array? It sounds like you're just changing it because it > > > pattern-matched on "array of length 1 at the end of a struct". > > > > Yeah; I should have changed that 'dynamically' part of the text above > > a bit. However, as I commented in the text below, in the case that more > > CS IDs are needed (let's wait for the maintainers to comment on this...) > > in the future, this change makes the code more maintainable, as for > > the allocation part, the developer would only have to update the CS_N > > macro to the number of CS IDs that are needed. > > But in that case, shouldn't you change it to "int cs[CS_N]" and get > rid of the struct_size() stuff? I do agree with Jann, I think it's best to consider this a fixed-size array for now. If we ever want to extend the number of supported CS, there is much more rework involved anyway. Thanks, Miquèl