Re: [PATCH v5 4/5] docs: gpio: Add GPIO Aggregator documentation

[Geert Uytterhoeven]

Hi Randy,

On Tue, Feb 18, 2020 at 7:30 PM Randy Dunlap <address@hidden> wrote:
> On 2/18/20 7:18 AM, Geert Uytterhoeven wrote:
> > Document the GPIO Aggregator, and the two typical use-cases.
> >
> > Signed-off-by: Geert Uytterhoeven <address@hidden>

> > --- /dev/null
> > +++ b/Documentation/admin-guide/gpio/gpio-aggregator.rst
> > @@ -0,0 +1,102 @@
> > +.. SPDX-License-Identifier: GPL-2.0-only
> > +
> > +GPIO Aggregator
> > +===============
> > +
> > +The GPIO Aggregator allows to aggregate GPIOs, and expose them as a new
>
> "allows" really wants an object following the verb [although the kernel 
> sources
> and docs have many cases of it not having an object].  Something like
>
>                        allows {you, one, someone, users, a user} to aggregate

Changing to:

    provides a mechanism to aggregate GPIOs

> > +gpio_chip.  This supports the following use cases.
> > +
> > +
> > +Aggregating GPIOs using Sysfs
> > +-----------------------------
> > +
> > +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.
> > +
> > +The GPIO Aggregator allows access control for individual GPIOs, by 
> > aggregating

Changing to:

    provides access control for a set of one or more GPIOs

> > +them into a new gpio_chip, which can be assigned to a group or user using
> > +standard UNIX file ownership and permissions.  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.

> > +Generic GPIO Driver
> > +-------------------
> > +
> > +The GPIO Aggregator can also be used as a generic driver for a simple
> > +GPIO-operated device described in DT, without a dedicated in-kernel driver.
> > +This is useful in industrial control, and is not unlike e.g. spidev, which
> > +allows to communicate with an SPI device from userspace.
>
>    allows {choose an object} to communicate

Changing to:

    allows the user to communicate

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- address@hidden

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