Re: GPIO Character device driver

[Linus Walleij <linus.walleij@xxxxxxxxxx>]

On Tue, Apr 23, 2019 at 2:57 PM gianluca <gianlucarenzi@xxxxxxxx> wrote:

> I was wondering on how to enable the gpio chardev. I have already
> installed the gpiolib (libgpiod-1.1.1) and my device tree has already
> some gpios configured as they are working with sysfs.
>
> Do I have to __DISABLE__ the sysfs support from kernel config?

No.

> Which module is working as the udev entry point for creating those
> /dev/gpiochip[X] device drivers?

Do you mean that they do not appear? I always had them appear
for me using udev, older busybox (mdev) had a problem but I
went in and fixed it so this should be there now.

/dev/gpiochipN even appears on my Intel laptop.

> The documentation is lacking those information. It seems I can have
> sysfs and gpiolib at the same time...

You can.

> P.S.: my boards are based with iMX6 and iMX28 SoC and they are running
> kernel 4.9.76 and 4.12. They are running Debian Stretch. The device-tree
> are modified from bootloader and passed to the kernel with some devices
> enabled.

Weird, I don't know my ways around userspace much though, sorry!
The problem would be the same with any such chardev such
as IIO devices though.

Yours,
Linus Walleij