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From:   Andy Shevchenko <andy.shevchenko@gmail.com>
Date:   Thu, 27 Apr 2023 13:46:01 +0300
Message-ID: <CAHp75VezDMZkRTRHRACtJZCW2S_1NoZL5GDK7tmA2vzjrAhOKg@mail.gmail.com>
Subject: Re: [PATCH] gpiolib: fix allocation of mixed dynamic/static GPIOs
To:     Andreas Kemnade <andreas@kemnade.info>
Cc:     Christophe Leroy <christophe.leroy@csgroup.eu>,
        "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 1:37=E2=80=AFPM Andreas Kemnade <andreas@kemnade.in=
fo> wrote:
>
> On Thu, 27 Apr 2023 06:20:34 +0000
> Christophe Leroy <christophe.leroy@csgroup.eu> wrote:
>
> > Le 27/04/2023 =C3=A0 08:00, Andy Shevchenko a =C3=A9crit :
> > > 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/LearnAbout=
SenderIdentification ]
> > >>>
> > >>> 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 suppos=
ed
> > >> 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.
> >
> > Ah right, that needs to be fixed.
> >
> > >
> > > 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.
> > >
> >
> > Yes you are right, that's gdev->base + gdev->ngpio that should be check=
ed.
> >
> and that not with simple continue or base might simply stay at DYNAMIC_BA=
SE.
>
> I will send a v2 of this patch with refined logic.

Actually it would be nice to integrate a warning (if we don't have it
yet) when adding a GPIO chip with a static allocation and which will
overlap the dynamic base. Can you add that into your v2?


--=20
With Best Regards,
Andy Shevchenko