For completeness sake, I'm posting the relevant code that now has fixed my original problem. I can now use an external library that has ISR (Interrupt Service Routine) capability.

What I needed to do was allow a user to send in a Perl code reference, and then have the C interrupt handler dynamically call that user-supplied sub when the interrupt occurred.

XS code that sets up the interrupt through the external lib:

void interruptHandler();
int setInterrupt(int pin, int edge, char *callback);

char *perl_callback;
PerlInterpreter *mine;

void interruptHandler(){
    PERL_SET_CONTEXT(mine);

    dSP;
    PUSHMARK(SP);
    PUTBACK;

    call_pv(perl_callback, G_DISCARD|G_NOARGS);

    FREETMPS;
    LEAVE;
}

int setInterrupt(int pin, int edge, char *callback){
    perl_callback = callback;
    int interrupt = wiringPiISR(pin, edge, &interruptHandler);
    return interrupt;
}

# XS

int
setInterrupt(pin, edge, callback)
    int pin
    int edge
    char *callback

void
interruptHandler()

[download]

Perl module code that calls into the XS:

sub set_interrupt {
    shift if @_ == 4;
    my ($pin, $edge, $callback) = @_;
    setInterrupt($pin, $edge, $callback);
}

[download]

...and finally a basic test script:

use warnings;
use strict;

use RPi::WiringPi;
use RPi::WiringPi::Constant qw(:all);

my $pi = RPi::WiringPi->new();
my $pin = $pi->pin(27);

RPi::WiringPi::Core::set_interrupt(
    $pin->num, 
    EDGE_RISING, 
    'pin_27_edge_rise'
);

$pin->mode(INPUT);

sleep 10;

# manually change the pin state here to trigger
# interrupt

$pi->cleanup;

sub pin_27_edge_rise {
    print "pin 27 edge rise callback...\n";
    # do other stuff
}

[download]

In reply to Re: XS: Passing an external library's function a Perl XS callback by stevieb
in thread SOLVED: XS: Passing an external library's function a Perl XS callback by stevieb

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