Re: A problem with gpios on my sunxi board.

[Kent Gibson <warthog618@gmail.com>]

On Mon, Jan 31, 2022 at 01:26:36PM +0200, Andy Shevchenko wrote:
> 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?
> 

Turns out not to be the case here, but the results wont be "way wrong"
- the ioctl call will just fail as it doesn't exist in the kernel.
Unfortunately that returns a generic EINVAL that can't be distinquished
from other causes of the same error.

Cheers,
Kent.