Re: A problem with gpios on my sunxi board.

[Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>]

On Mon, Jan 31, 2022 at 08:59:24AM +0800, Kent Gibson wrote:
> On Fri, Jan 28, 2022 at 10:12:13PM +0800, Gasai Maple wrote:
> > I posted a question on stackoverflow, it's basically about me having
> > problems operating gpio with libgpiod, and a user advised me to drop a
> > message, the link is here
> > https://stackoverflow.com/questions/70863283/libgpiod-tests-fails-on-pcduino3-nano
> 
> It would be helpful to restate your question rather than providing the
> link.  But anyway...
> 
> My best guess is that your kernel is built with only v2 of the GPIO CDEV ABI.
> libgpiod support for v2 is a WIP, and 1.6.3 only supports ABI v1.
> The CHIP_INFO ioctl is common to both, so will still work.
> But all the line request ioctls changed so they wont.
> So libgpiod is probably making ioctl calls that your kernel doesn't
> support.

If this the case, can we add some warning to libgpiod tools to tell user that
the results may be way wrong because of that?

> For compatibility with libgpiod v1.6.3, ensure your kernel is built with
> these options:
> 
> CONFIG_GPIO_CDEV=y
> CONFIG_GPIO_CDEV_V1=y
> 
> And the libgpiod tests require that gpio-mockup is available as a loadable
> module, so
> 
> CONFIG_GPIO_MOCKUP=m
> 
> If building a new kernel isn't an option for you then you might want to
> try the development branch of libgpiod[1].
> Or you could try my Go[2] or Rust[3] libraries that both support both
> versions of the ABI and provide tools equivalent to libgpiod.
> 
> If you still have issues, try using strace to display the ioctl calls and
> we can debug that.
> 
> Cheers,
> Kent.
> 
> [1] https://git.kernel.org/pub/scm/libs/libgpiod/libgpiod.git/log/?h=next/libgpiod-2.0
> [2] https://github.com/warthog618/gpiod
> [3] https://github.com/warthog618/gpiod-rs

-- 
With Best Regards,
Andy Shevchenko