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References: <20230426220338.430638-1-andreas@kemnade.info> <f6b261ad-3267-db70-c173-154a12c42bea@csgroup.eu>
In-Reply-To: <f6b261ad-3267-db70-c173-154a12c42bea@csgroup.eu>
From:   Andy Shevchenko <andy.shevchenko@gmail.com>
Date:   Thu, 27 Apr 2023 09:00:47 +0300
Message-ID: <CAHp75Vep8VSirY7mvGGCubNi-O4jS_inTALS3Ei9mQu98RV+7Q@mail.gmail.com>
Subject: Re: [PATCH] gpiolib: fix allocation of mixed dynamic/static GPIOs
To:     Christophe Leroy <christophe.leroy@csgroup.eu>
Cc:     Andreas Kemnade <andreas@kemnade.info>,
        "linus.walleij@linaro.org" <linus.walleij@linaro.org>,
        "brgl@bgdev.pl" <brgl@bgdev.pl>,
        "linux-gpio@vger.kernel.org" <linux-gpio@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        ": Tony Lindgren" <tony@atomide.com>,
        Aaro Koskinen <aaro.koskinen@iki.fi>,
        "linux-omap@vger.kernel.org" <linux-omap@vger.kernel.org>
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On Thu, Apr 27, 2023 at 8:40=E2=80=AFAM Christophe Leroy
<christophe.leroy@csgroup.eu> wrote:
>
>
>
> Le 27/04/2023 =C3=A0 00:03, Andreas Kemnade a =C3=A9crit :
> > [Vous ne recevez pas souvent de courriers de andreas@kemnade.info. D=C3=
=A9couvrez pourquoi ceci est important =C3=A0 https://aka.ms/LearnAboutSend=
erIdentification ]
> >
> > If static allocation and dynamic allocation GPIOs are present,
> > dynamic allocation pollutes the numberspace for static allocation,
> > causing static allocation to fail.
> > Enfore dynamic allocation above GPIO_DYNAMIC_BASE.
>
> Hum ....
>
> Commit 7b61212f2a07 ("gpiolib: Get rid of ARCH_NR_GPIOS") was supposed
> to enforce dynamic allocation above GPIO_DYNAMIC_BASE already.
>
> Can you describe what is going wrong exactly with the above commit ?

Above commit only works to the first dynamic allocation, if you need
more than one with static ones present it mistakenly will give you a
base _below_ DYNAMIC_BASE.

However, this change is just PoC I proposed, the conditional and
action should be slightly different to cover a corner case, when
statically allocated chip overlaps the DYNAMIC_BASE, i.e. gdev->base <
DYNAMIC_BASE, while gdev->base + gdev->ngpio >=3D DYNAMIC_BASE.


--=20
With Best Regards,
Andy Shevchenko