Re: Elegant way to kill previous gpioset?

[Leszek Dubiel <leszek@xxxxxxxxx>]

> The best way is not to have to kill it.
> If you kill the gpioset then the state of the line becomes indeterminate
> so you are open to glitches as well as some other process grabbing the
> line.

Yes, that's true.



> To address this the gpioset for v2[1] has an interactive mode that allows
> you to pipe commands to it.  The tests for v2[2] (gpio-tools-tests.bats)
> demonstrate that by launching the gpioset from bash using coproc and then
> driving the gpioset via the pipe to the co-process.
> For a more long lived solution you can setup a named pipe and then write
> commands to that to update the line:
>
> mkfifo setpipe
> gpioset --interactive -c gpiochip2 7=0 < setpipe &
> echo "set 7=1" > setpipe
> or
> echo "toggle" > setpipe
>
> You can even kill it with:
>
> echo "exit" > setpipe

I have tried pipe even in current gpioset tools, because if I
hit Enter then it gpioset exits. Similar as last line above.

Thanks to your explanation I know what's the
intention behind "--interactive" option.





> Would that work for you?

I was wondering if there is some "one-liner" that
recofigures pin, something like:

                gpioset -b -msignal --autokill /dev/gpiochip2 7=0

or
                gpioset -b -msignal --force /dev/gpiochip2 7=0

that does these two commands at once:

              pkill -ef "^gpioset .* /dev/gpiochip2 7=[01]$"
              gpioset -b -msignal /dev/gpiochip2 7=0



New tools with "setpipe" and "--interactive" would
do the job too. :) :)






> Personally, for situations like this I don't use the tools, I use one of
> the bindings to write a daemon that controls the line and receives its
> commands from some other source.
>
> There are plans for a generic daemon that would allow you to access lines
> via dbus, but that hasn't got past the planning stages AFAIAA.
>
> Wrt identifying and killing processes holding particular lines,
> the ability to identify the GPIO lines held by processes via the /proc
> filesystem has recently been added to the 6.1 kernel[3].  There are
> plans for a tool that will use that to return the PID holding a line,
> but again that is still in the planning stages.


Thank you for detailed explanation.