linux-kernel - Re: [PATCH] gpiolib: fix allocation of mixed dynamic/static GPIOs

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Date:   Thu, 27 Apr 2023 06:20:34 +0000
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
CC:     Andreas Kemnade <andreas@...nade.info>,
        "linus.walleij@...aro.org" <linus.walleij@...aro.org>,
        "brgl@...ev.pl" <brgl@...ev.pl>,
        "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        ": Tony Lindgren" <tony@...mide.com>,
        Aaro Koskinen <aaro.koskinen@....fi>,
        "linux-omap@...r.kernel.org" <linux-omap@...r.kernel.org>
Subject: Re: [PATCH] gpiolib: fix allocation of mixed dynamic/static GPIOs



Le 27/04/2023 à 08:00, Andy Shevchenko a écrit :
> On Thu, Apr 27, 2023 at 8:40 AM Christophe Leroy
> <christophe.leroy@...roup.eu> wrote:
>>
>>
>>
>> Le 27/04/2023 à 00:03, Andreas Kemnade a écrit :
>>> [Vous ne recevez pas souvent de courriers de andreas@...nade.info. Découvrez pourquoi ceci est important à https://aka.ms/LearnAboutSenderIdentification ]
>>>
>>> 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.

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 >= DYNAMIC_BASE.
> 

Yes you are right, that's gdev->base + gdev->ngpio that should be checked.

Christophe