Re: Edit/gpiomon: Question about mode

[Hans Kurscheidt <lve0200@gmail.com>]

Am 29.03.2022 um 10:38 schrieb Kent Gibson:
> 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.

So if I understand you right, gpiod works on sort of a logical level, 
while the HW dependend part depends of the kernel driver implementation 
of the specific HW?