Messages in this thread | | | From | Linus Walleij <> | Date | Sat, 4 Jan 2020 01:38:38 +0100 | Subject | Re: [PATCH v3 5/7] gpio: Add GPIO Aggregator/Repeater driver |
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Sorry for slowness... christmas.
On Thu, Dec 12, 2019 at 4:24 PM Geert Uytterhoeven <geert@linux-m68k.org> wrote: > On Thu, Dec 12, 2019 at 3:34 PM Linus Walleij <linus.walleij@linaro.org> wrote:
> > > + This can serve the following purposes: > > > + 1. Assign a collection of GPIOs to a user, or export them to a > > > + virtual machine, > > > > This is ambiguous. What is a "user"? A process calling from > > userspace? A device tree node? > > A user is an entity with a UID, typically listed in /etc/passwd. > This is similar to letting some, not all, people on the machine access > the CD-ROM drive.
Ah I get it. Maybe we can say "assign permissions for a collection of GPIOs to a user".
> > I would write "assign a collection of GPIO lines from any lines on > > existing physical GPIO chips to form a new virtual GPIO chip" > > > > That should be to the point, right? > > Yes, that's WHAT it does. The WHY is the granular access control.
So I guess we can write both?
> > > + 3. Provide a generic driver for a GPIO-operated device, to be > > > + controlled from userspace using the GPIO chardev interface. > > > > I don't understand this, it needs to be elaborated. What is meant > > by a "GPIO-operated device" in this context? Example? > > E.g. a motor. Or a door opener. > > door-opener { > compatible = "mydoor,opener"; > > gpios = <&gpio2 19 GPIO_ACTIVE_HIGH>; > }; > > You don't need a full-featured kernel driver for that, so just bind the > gpio-aggregator to the door-opener, and control it through libgpiod.
Yep it's a perfect industrial control example, I get it.
Maybe we should blurb something about industrial control?
The rest I think we cleared out else I will see it when I review again.
Yours, Linus Walleij
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