Re: [libgpiod]

[Bartosz Golaszewski <brgl@xxxxxxxx>]

pon., 10 lut 2020 o 11:46 Geoffrey White <geoffrey@xxxxxxxxxxxxxx> napisał(a):
>
> Hello,
>
> What a great library gpiod is. I am trying to port over my robot
> software from WiringPi to it at the moment.  I am running Ubuntu 18.04
> on both a development laptop and a Raspbery Pi 3 A+. I cross compile
> version 1.4.2 and can run on the Pi and iterate over the detected
> devices fine. However I'm not able to detect the correct chipset on
> the device.
>
> The Pi v3a+ uses the Broadcom chipset BCM2837B0, however the chip is
> detected as a bcm2835 which is from the original Pi v1. Further, none
> of the lines are labelled with a description. They all appear as
> "unnamed" instead of labels such as  "GPIO_GCLK" or "GPIO17"
>

Hi!

I don't have an RPi3A+ (or any RPi for that matter) but just a quick
look at the relevant device tree in upstream kernel is telling me that
the compatible used for the GPIO controller is "brcm,bcm2835-gpio" for
which the driver should introduce itself as "pinctrl-bcm2835". And
it's fine - maybe it's the same old pinctrl IP in the newer SoC?

As for the pin descriptions: libgpiod only extracts data provided by
the kernel and I have never received reports of this feature not
working before. I'd look for the problem in the kernel first. In
mainline linux I can see all the pins having names though.

Bartosz

> I heard the stock Kernel. on 18.04 (4.15) did have some issues,
> however I have since upgraded to the 5.3.0 Kernal on both my dev
> laptop and Pi.
>
> I would personally like to keep to using the Ubuntu distribution for
> the Pi, however perhaps it is better i revert back to Raspbian.
>
> My future work I hope to integrate the DMA timing for a simple PWM
> control using the gpiod, i'd like to help out with the project if I
> can, sorry if I have approached the wrong email list.
>
>  Regards,
>
> Geoffrey.