is_usbtmc_parent

#!/usr/bin/perl
# find if usb device is 'parent' to a usbtmc device
# returns 'true' (exit 0) if so

# Assumes that usb device is something like:
#    (stuff)/usb1/1-3
# and that the child device is something like:
#    (stuff)/usb1/1-3/1-3:2.4
# identified as a usbtmc device by having "DRIVER=usbtmc" in its uevent file.
#

# There might be a more elegant solution using udevadm, but didn't find it.
my $DEBUG = 0;
open(D,">>/var/log/usbtmc.log") if $DEBUG;

$devpath=$ENV{'DEVPATH'};
$devpath=shift if $DEBUG && !defined($devpath);

print D "devpath = $devpath\n" if $DEBUG;

exit 1 unless $devpath =~ /\/usb\d+\/(\d+\-\d+)$/;
my $tag  = $1;
print D "got usb devpath tag $tag\n"  if $DEBUG;

open(X,"find /sys${devpath} -maxdepth 2 -mindepth 2 -name uevent|") || die "find problem";
while (<X>) {
    chomp;
    next unless /$tag\/$tag:\d+\.\d+\/uevent/;
    print D "uevent file $_\n" if $DEBUG;
    $uev = $_;
    open(Y,"<$uev") || die "error opening $uev";
    while (<Y>) {
        chomp;
        next unless /^DRIVER=usbtmc\s*$/;
        print D "got usbtmc child device\n" if $DEBUG;
        exit 0;
    }
    close(Y);
}
close(X);
print D "not a usbtmc parent device\n" if $DEBUG;
exit 1;