Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
MIME-Version: 1.0
References: <20200930210824.GA12277@embeddedor> <CAG48ez3X3aZwfde3_2Sc+gdtUGRHfzan6oNFiffAvNzFDSsFDw@mail.gmail.com>
 <20200930213634.GA12855@embeddedor>
In-Reply-To: <20200930213634.GA12855@embeddedor>
From:   Jann Horn <jannh@google.com>
Date:   Thu, 1 Oct 2020 00:32:24 +0200
Message-ID: <CAG48ez3XqE0m2UmRh+OtmYJRhyCBYY=sdJKaWBXtJZKCRpLMYQ@mail.gmail.com>
Subject: Re: [PATCH][next] mtd: rawnand: Replace one-element array with
 flexible-array member
To:     "Gustavo A. R. Silva" <gustavoars@kernel.org>
Cc:     Stefan Agner <stefan@agner.ch>, Lucas Stach <dev@lynxeye.de>,
        Miquel Raynal <miquel.raynal@bootlin.com>,
        Richard Weinberger <richard@nod.at>,
        Vignesh Raghavendra <vigneshr@ti.com>,
        Thierry Reding <thierry.reding@gmail.com>,
        Jonathan Hunter <jonathanh@nvidia.com>,
        linux-mtd@lists.infradead.org, linux-tegra@vger.kernel.org,
        kernel list <linux-kernel@vger.kernel.org>,
        linux-hardening@vger.kernel.org
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
Precedence: bulk

On Wed, Sep 30, 2020 at 11:30 PM Gustavo A. R. Silva
<gustavoars@kernel.org> 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
> > <gustavoars@kernel.org> wrote:
> > > There is a regular need in the kernel to provide a way to declare hav=
ing
> > > a dynamically sized set of trailing elements in a structure. Kernel c=
ode
> > > should always use =E2=80=9Cflexible array members=E2=80=9D[1] for the=
se 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?