Re: [RFC] gpio: expose pull-up/pull-down line flags to userspace

[Drew Fustini <pdp7pdp7@xxxxxxxxx>]

On Thu, Oct 10, 2019 at 1:59 AM Kent Gibson <warthog618@xxxxxxxxx> wrote:
> It is basically working for me on my Pi4:
>
> pi@quoll:~ $ ./gpiodctl get gpiochip0 7
> 0
> pi@quoll:~ $ ./gpiodctl get -u gpiochip0 7
> 1
> pi@quoll:~ $ ./gpiodctl get gpiochip0 7
> 1
> pi@quoll:~ $ ./gpiodctl get -d gpiochip0 7
> 0
> pi@quoll:~ $ ./gpiodctl get gpiochip0 7
> 0
>
> That is using the gpiodctl tool from my gpiod library.
> My gpiod test suite also passes, but it doesn't do much to
> exercise the UAPI.
> I was intending to run my uapi test suite, which is more thorough,
> but it turns out that only targets gpio-mockup, whereas my gpiod
> test suite can target either.
> Something else for the todo list.
>
> Hopefully it is obvious what gpiodctl is doing. (-u sets the
> pull-up flag, -d sets the pull-down flag)
> Looks like the pulls stick when the line is released, and the
> subsequent get, without pull-up set, either doesn't clear the
> pull-up/down or the line stays floating at the old pull level.
> More investigation required, but that will have to wait til
> I get back to this later in the day.
>
> Oh, and that is running on the rpi-5.3.3 kernel patched with everything
> on my topic/gpio-uapi-config branch from 5.4-rc2 onward.

Thanks for sharing your results.

My Pi 3 had been running 5.3.0-v7+ from September 20th with my
pull-up/down patch (82fc38f6ab59).

I removed that patch and just cross-compiled 5.4-rc2 with
multi_v7_defconfig for the Pi3.

Are these the commits that I should apply from your topic branch?

bdc9696a27ed pull up/down requires explicit input mode in lineevent_create
14ee636232d4 disallow pull up/down on outputs
ce03bf5af1ec implement SET_CONFIG_IOCTL
f38b7554eb52 pull common validation code into linehandle_validate_flags
31c0aa53ffc3 Add default values for setting output
3c7ec03efcd9 add support for pull up/down to lineevent_create
99b85d1c26ea gpio: add new ioctl() to gpio chardev
82fc38f6ab59 gpio: expose pull-up/pull-down line flags to userspace
f6cfbbe2950b gpiolib: sanitize flags before allocating memory in
lineevent_create()

Thanks,
Drew