SV: [PATCH RFC] gpio: new driver for a gpio simulator

[Einar Vading <einar.vading@axis.com>]

Since I was just evaluating the mockup driver to use in a test setup I'll give my 2 cents.

The benefit of the simulator is that we get the possibility to, if I understand correctly, monitor an input for changes on the connected output. Sure, we could also use ftrace but I like the idea of having the two connected GPIOs. As a matter of fact I was just thinking about implementing something that gave the same functionality for the mockup driver.

What I like from the mockup driver is the possibility to have *many* gpios on the same chip. We currently have a MCU I/O expander that gives us 110+ gpios. So for us 64 GPIOs is really not enough.

So neither driver works out of the box for us right now but both looks very promising.

Best Regards
Einar
________________________________________
Från: linux-gpio-owner@vger.kernel.org <linux-gpio-owner@vger.kernel.org> för Vincent Whitchurch <rabinv@axis.com>
Skickat: den 11 oktober 2018 11:49
Till: Uwe Kleine-König
Kopia: Linus Walleij; Bartosz Golaszewski; Mark Rutland; open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS; open list:GPIO SUBSYSTEM; Rob Herring; Sascha Hauer
Ämne: Re: [PATCH RFC] gpio: new driver for a gpio simulator

On Thu, Oct 11, 2018 at 10:16:46AM +0200, Uwe Kleine-König wrote:
> @Vincent: What is your usecase? I currently cannot imagine a use case
> that can be done with the mockup driver but not with the simulator.

I just needed a fake GPIO chip with a bunch of pins that I could use
before I got the hardware with a real GPIO expander.  In my case I only
needed to test output so IIRC I didn't use the debugfs interface at all
but instead used ftrace to check that my userspace triggered the correct
operations on the "pins".

So, yes, that would probably have worked just as well with this
simulator instead of the mockup driver.