Re: Edit/gpiomon: Question about mode

[Hans Kurscheidt <lve0200@gmail.com>]

Am 29.03.2022 um 10:51 schrieb Kent Gibson:
> On Tue, Mar 29, 2022 at 10:43:19AM +0200, Hans Kurscheidt wrote:
>> 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?
>>
>>
> libgpiod is a userspace library and tools to access GPIO lines via the
> Linux GPIO character device.  The actual interfacing to the hardware is
> performed by the kernel and appropriate drivers for your hardware.
> As your problem does not exhibit on other hardware, the root cause
> of your problem probably lies in the driver for your hardware, not in
> libgpiod nor the gpiolib subsystem of the kernel.
>
> But you would need to debug it further to be sure.
>
> Cheers,
> Kent.


OK, thank's. I'll raise a bug report for the OPI kernel guys in the 
ARMBIAN forum.