linux-kernel - Re: [PATCH] lib: devres: add a comment about the devm_of

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Message-ID: <CAK8P3a0TivBERWMZcs8Kndb4=Fc41JH6vkxJzMp1FHsazvLfdQ@mail.gmail.com>
Date:   Tue, 9 Jun 2020 16:20:09 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Dan Carpenter <dan.carpenter@...cle.com>
Cc:     Aisheng Dong <aisheng.dong@....com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Tuowen Zhao <ztuowen@...il.com>,
        Denis Efremov <efremov@...ux.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        kernel-janitors@...r.kernel.org,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        BOUGH CHEN <haibo.chen@....com>,
        "festevam@...il.com" <festevam@...il.com>,
        "shawnguo@...nel.org" <shawnguo@...nel.org>,
        "stefan@...er.ch" <stefan@...er.ch>,
        "kernel@...gutronix.de" <kernel@...gutronix.de>,
        "linus.walleij@...aro.org" <linus.walleij@...aro.org>,
        "s.hauer@...gutronix.de" <s.hauer@...gutronix.de>,
        dl-linux-imx <linux-imx@....com>,
        Christophe JAILLET <christophe.jaillet@...adoo.fr>,
        "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>
Subject: Re: [PATCH] lib: devres: add a comment about the devm_of_iomap() function

On Tue, Jun 9, 2020 at 12:47 PM Dan Carpenter <dan.carpenter@...cle.com> wrote:
>
> We recently introduced a bug when we tried to convert of_iomap() to
> devm_of_iomap().  The problem was that there were two drivers mapping
> the same io region.  The first driver was using of_iomap() and the
> second driver was using devm_of_iomap() and the kernel booted fine.
> When we converted the first drive to use devm_of_iomap() then the second
> driver failed with -EBUSY and the kernel couldn't boot.
>
> Let's add a comment to prevent this sort of mistake in the future.
>
> Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>

Good idea,

Acked-by: Arnd Bergmann <arnd@...db.de>