linux-kernel - Re: [PATCH v2 04/12] gpio: acpi: Even more tighten up ACPI GPIO lookups

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Date:   Mon, 29 May 2017 11:18:17 +0200
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Hans de Goede <hdegoede@...hat.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Jarkko Nikula <jarkko.nikula@...ux.intel.com>,
        Jagadish Krishnamoorthy <jagadish.krishnamoorthy@...el.com>,
        Bastien Nocera <hadess@...ess.net>
Subject: Re: [PATCH v2 04/12] gpio: acpi: Even more tighten up ACPI GPIO lookups

On Tue, May 23, 2017 at 7:03 PM, Andy Shevchenko
<andriy.shevchenko@...ux.intel.com> wrote:

> The commit 10cf4899f8af ("gpiolib: tighten up ACPI legacy gpio lookups")
> prevents to getting same resource twice if the driver asks twice using
> different connection ID.
>
> But the whole idea of fallback might bring some problems. Imagine the case when
> we have two versions of BIOS/hardware where in one _DSD is introduced along
> with GPIO resources, but the other one uses just plain GPIO resource for
> another purpose
>
> Case 1:
>
>     Device (DEVX)
>     {
>         ...
>         Name (_CRS, ResourceTemplate ()
>         {
>             GpioIo (Exclusive, PullUp, 0, 0, IoRestrictionInputOnly,
>                     "\\_SB.GPO0", 0, ResourceConsumer) {15}
>         })
>         Name (_DSD, Package ()
>         {
>             ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
>             Package ()
>             {
>                 Package () {"some-gpios", Package() {^DEVX, 0, 0, 0 }},
>             }
>         })
>     }
>
> Case 2:
>
>     Device (DEVX)
>     {
>         ...
>         Name (_CRS, ResourceTemplate ()
>         {
>             GpioIo (Exclusive, PullUp, 0, 0, IoRestrictionInputOnly,
>                     "\\_SB.GPO0", 0, ResourceConsumer) {27}
>         })
>     }
>
> To prevent the possible misconfiguration tighten up even more GPIO ACPI lookups
> for case without connection ID provided.
>
> In the past the issue had been triggered by "use mctrl_gpio helpers" series
> [1,2].
>
> [1] commit 4ef03d328769 ("tty/serial/8250: use mctrl_gpio helpers")
> [2] https://patchwork.kernel.org/patch/9283745/
>
> Cc: Dmitry Torokhov <dmitry.torokhov@...il.com>
> Cc: Bastien Nocera <hadess@...ess.net>
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> Tested-by: Jarkko Nikula <jarkko.nikula@...ux.intel.com>
> Reviewed-by: Mika Westerberg <mika.westerberg@...ux.intel.com>

Patch applied.

Yours,
Linus Walleij