LKML Archive on lore.kernel.org
 help / color / Atom feed
From: Geert Uytterhoeven <geert@linux-m68k.org>
To: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Cc: Geert Uytterhoeven <geert+renesas@glider.be>,
	Linus Walleij <linus.walleij@linaro.org>,
	Alexander Graf <agraf@suse.de>,
	Peter Maydell <peter.maydell@linaro.org>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Magnus Damm <magnus.damm@gmail.com>,
	linux-gpio <linux-gpio@vger.kernel.org>,
	QEMU Developers <qemu-devel@nongnu.org>,
	Linux-Renesas <linux-renesas-soc@vger.kernel.org>,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH RFC] gpio: Add Virtual Aggregator GPIO Driver
Date: Tue, 9 Jul 2019 17:59:47 +0200
Message-ID: <CAMuHMdUkF32+wOLkfd2BL4h-=0nZjPDMtVOpOcyDYzBbhWXteQ@mail.gmail.com> (raw)
In-Reply-To: <CAMpxmJUF1s1zyXVtoUGfbV7Yk+heua4rNjY=DrX=jr-v8UfNxA@mail.gmail.com>

Hi Bartosz,

On Tue, Jul 9, 2019 at 4:59 PM Bartosz Golaszewski
<bgolaszewski@baylibre.com> wrote:
> pon., 8 lip 2019 o 12:24 Geert Uytterhoeven <geert@linux-m68k.org> napisał(a):
> > On Mon, Jul 8, 2019 at 11:45 AM Bartosz Golaszewski
> > <bgolaszewski@baylibre.com> wrote:
> > > pt., 5 lip 2019 o 18:05 Geert Uytterhoeven <geert+renesas@glider.be> napisał(a):
> > > > 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 add a virtual GPIO driver to aggregate existing GPIOs (up to 32),
> > > > 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, it would simplify and harden exporting GPIOs to a virtual
> > > > machine, as the VM can just grab the full virtual GPIO controller, and
> > > > no longer needs to care about which GPIOs to grab and which not,
> > > > reducing the attack surface.
> > > >
> > > > Virtual GPIO controllers are instantiated by writing to the "new_device"
> > > > attribute file in sysfs:
> > > >
> > > >     $ echo "<gpiochipA> <gpioA1> [<gpioA2> ...]"
> > > >            "[, <gpiochipB> <gpioB1> [<gpioB2> ...]] ...]"
> > > >             > /sys/bus/platform/drivers/gpio-virt-agg/new_device
> > > >
> > > > Likewise, virtual GPIO controllers can be destroyed after use:
> > > >
> > > >     $ echo gpio-virt-agg.<N> \
> > > >             > /sys/bus/platform/drivers/gpio-virt-agg/delete_device

> Am I doing it right? I'm trying to create a device and am only getting this:
>
> # echo gpiochip2 23 > new_device
> [  707.507039] gpio-virt-agg gpio-virt-agg.0: Cannot find gpiochip gpiochip2
>
> gpiochip2 *does* exist in the system.

Please try the name of the platform device instead.
I.e. for my koelsch (R-Car M2-W), it needs "e6052000.gpio" instead
of "gpiochip2".

Probably the driver should match on both.

> I see. I'll try to review it more thoroughly once I get to play with
> it. So far I'm stuck on creating the virtual chip.

Thanks, good luck!

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

  reply index

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-07-05 16:05 Geert Uytterhoeven
2019-07-08  9:44 ` Bartosz Golaszewski
2019-07-08 10:24   ` Geert Uytterhoeven
2019-07-09 14:58     ` Bartosz Golaszewski
2019-07-09 15:59       ` Geert Uytterhoeven [this message]
2019-07-12  9:27         ` Bartosz Golaszewski
2019-09-06 11:14           ` Geert Uytterhoeven
2019-09-06 11:09       ` Geert Uytterhoeven
2019-07-10  2:00 ` Phil Reid
2019-07-10 10:21   ` Geert Uytterhoeven
2019-07-11  9:24     ` Phil Reid
2019-07-11  9:54       ` Geert Uytterhoeven
2019-08-01  8:41 ` Linus Walleij
2019-08-05 10:21   ` Marc Zyngier
2019-08-05 10:56     ` Linus Walleij
2019-09-12  8:56 ` Linus Walleij
2019-09-12  8:59   ` Geert Uytterhoeven

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to='CAMuHMdUkF32+wOLkfd2BL4h-=0nZjPDMtVOpOcyDYzBbhWXteQ@mail.gmail.com' \
    --to=geert@linux-m68k.org \
    --cc=agraf@suse.de \
    --cc=bgolaszewski@baylibre.com \
    --cc=geert+renesas@glider.be \
    --cc=linus.walleij@linaro.org \
    --cc=linux-gpio@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-renesas-soc@vger.kernel.org \
    --cc=magnus.damm@gmail.com \
    --cc=pbonzini@redhat.com \
    --cc=peter.maydell@linaro.org \
    --cc=qemu-devel@nongnu.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

LKML Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/lkml/0 lkml/git/0.git
	git clone --mirror https://lore.kernel.org/lkml/1 lkml/git/1.git
	git clone --mirror https://lore.kernel.org/lkml/2 lkml/git/2.git
	git clone --mirror https://lore.kernel.org/lkml/3 lkml/git/3.git
	git clone --mirror https://lore.kernel.org/lkml/4 lkml/git/4.git
	git clone --mirror https://lore.kernel.org/lkml/5 lkml/git/5.git
	git clone --mirror https://lore.kernel.org/lkml/6 lkml/git/6.git
	git clone --mirror https://lore.kernel.org/lkml/7 lkml/git/7.git
	git clone --mirror https://lore.kernel.org/lkml/8 lkml/git/8.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 lkml lkml/ https://lore.kernel.org/lkml \
		linux-kernel@vger.kernel.org
	public-inbox-index lkml

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-kernel


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git