Re: Edit/gpiomon: Question about mode

[Kent Gibson <warthog618@gmail.com>]

On Tue, Mar 29, 2022 at 10:07:57AM +0200, Hans Kurscheidt wrote:
> 
> Am 29.03.2022 um 05:38 schrieb Kent Gibson:
> > On Mon, Mar 28, 2022 at 07:13:13PM +0200, Hans Kurscheidt wrote:
> > > Am 28.03.2022 um 15:16 schrieb Hans Kurscheidt:
> > > > Hi,
> > > > 
> > > > what would be the right mode for gpiomon call from
> > > > 
> > > > a shellscript executed as root from systemd at system start
> > > > 
> > > > waiting on a Pin w/ pullup for invoking shutdown upon rising* edge.
> > > > *changed
> > > > 
> > > > 
> > > > Lots of interupts, Signals and other GPIO ongoing from other user APPs &
> > > > threads in multi-user state.
> > > 2b more precise: I wired a GPIO Pin to GND.
> > > 
> > > Upon the cmd: sudo gpiomon -r -n1 <chip> <offset>
> > > 
> > > the program exits immediately with 1 event, although there was never a
> > > rising edge due to the fix wire to GND. Is this a feature or a bug, and is
> > > it reproducible?
> > > 
> > Not a feature and not reproducible for me on a Raspberry Pi4 with the
> > setup you describe, so probably a bug specific to your hardware platform,
> > whatever that may be.
> > 
> > If it is 100% reproduceable for you, and assuming it is an initialisation
> > issue so you only get the one spurious event, how about using -n2 as a
> > workaround ;-)?
> > 
> > Cheers,
> > Kent.
> 
> It appears 2b reproduceable 100% on my OrangePi zero+ (Allwinner H5) and
> using -n2 does the trick, but isn't gpiod not supposed to work on all
> commercial HW platforms and related kernels, rather then only on RPI??
> 

gpiod will work on any platform with a supporting kernel.
How well depends on the underlying hardware and driver.
The RPi4 was merely a counter-example demonstrating that your issue is
not universal, using hardware I happen to have readily available.

Cheers,
Kent.