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From:   Geert Uytterhoeven <geert@linux-m68k.org>
Date:   Fri, 21 Feb 2020 17:39:19 +0100
Message-ID: <CAMuHMdWo_JBpBeS72RkZBwuWyMhMj79=9ErFdXcLSqC2rOhJDg@mail.gmail.com>
Subject: Re: [PATCH v5 0/5] gpio: Add GPIO Aggregator
To:     Linus Walleij <linus.walleij@linaro.org>,
        Bartosz Golaszewski <bgolaszewski@baylibre.com>
Cc:     Jonathan Corbet <corbet@lwn.net>,
        Harish Jenny K N <harish_kandiga@mentor.com>,
        Eugeniu Rosca <erosca@de.adit-jv.com>,
        Alexander Graf <graf@amazon.com>,
        Peter Maydell <peter.maydell@linaro.org>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Phil Reid <preid@electromag.com.au>,
        Marc Zyngier <marc.zyngier@arm.com>,
        Christoffer Dall <christoffer.dall@arm.com>,
        Magnus Damm <magnus.damm@gmail.com>,
        Rob Herring <robh+dt@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@vger.kernel.org>,
        "open list:DOCUMENTATION" <linux-doc@vger.kernel.org>,
        Linux-Renesas <linux-renesas-soc@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        QEMU Developers <qemu-devel@nongnu.org>,
        Geert Uytterhoeven <geert+renesas@glider.be>
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Hi Linus and Bartosz,

On Tue, Feb 18, 2020 at 4:18 PM Geert Uytterhoeven
<geert+renesas@glider.be> wrote:
> GPIO controllers are exported to userspace using /dev/gpiochip*
> character devices.  Access control to these devices is provided by
> standard UNIX file system permissions, on an all-or-nothing basis:
> either a GPIO controller is accessible for a user, or it is not.
> Currently no mechanism exists to control access to individual GPIOs.
>
> Hence this adds a GPIO driver to aggregate existing GPIOs, and expose
> them as a new gpiochip.  This is useful for implementing access control,
> and assigning a set of GPIOs to a specific user.  Furthermore, this
> simplifies and hardens exporting GPIOs to a virtual machine, as the VM
> can just grab the full GPIO controller, and no longer needs to care
> about which GPIOs to grab and which not, reducing the attack surface.

Do you have any more comments, before I respin and post v6?

Thanks, and have a niec weekend!

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds