Add SCSI SENSE information to detect if the drive is in a low power s…

…tate, and avoid waking it

plugins/node.d/hddtemp_smartctl

@@ -152,6 +152,10 @@ if ($smartctl and `$smartctl --version` =~ / release (\d+\.\d+) /i) {
 my $hdparm = `sh -c 'command -v hdparm'`;
 chomp $hdparm;
 
+# sdparm is used for checking SENSE data
+my $sdparm = `sh -c 'command -v sdparm'`;
+chomp $sdparm;
+
 my @drives;
 
 # Try to get a default set of drives
@@ -235,6 +239,9 @@ if (defined $ARGV[0]) {
 foreach my $drive (@drives) {
   warn "[DEBUG] Processing $drive\n" if $DEBUG;
   my $fulldev = device_for_drive($drive);
+
+  # Don't wake up SCSI drives!
+  next if (check_scsi_low_power($fulldev));
 
   # Fall back to using hdparm for detecting disks in stand-by only if nocheck
   # isn't supported (hdparm isn't available on all platforms).
@@ -330,6 +337,9 @@ sub command_for_drive_device {
 sub get_drive_id {
     my ($drive, $fulldev, $use_nocheck) = @_;
 
+    # Don't wake up SCSI drives!
+    return '' if (check_scsi_low_power($fulldev));
+
     my $cmd = $smartctl.' -i ';
     $cmd .= '--nocheck=standby ' if $use_nocheck;
     $cmd .= $fulldev;
@@ -358,3 +368,35 @@ sub get_drive_id {
 
     return $id;
 }
+
+
+sub check_scsi_low_power {
+  my ($fulldev) = @_;
+
+  # If present, use sdparm to check the SENSE data to see if the drive is in low power mode
+  # This catches SCSI drives' low power modes, per https://www.t10.org/lists/asc-num.htm#ASC_5E
+
+  if ($sdparm) {
+    my @lines = `$sdparm --readonly --command=sense --hex $fulldev 2> /dev/null`;
+    # sdparm error cases (ie. ATA drives) should return 0, to be checked in other ways
+    return 0 if ($? != 0);
+
+    # get hex bytes
+    my @sensehexbytes = ();
+    foreach my $line(@lines) {
+        # strip off leading line/word indicators
+        $line =~ s/^\s+\d+\s+//;
+        # add hex bytes to our array
+        push(@sensehexbytes, $line =~ /([0-9a-f]{2})+/g);
+    }
+    # Check for 5e in the additional sense location (byte 13)
+    # https://www.t10.org/lists/asc-num.htm#ASC_5E
+    if (scalar @sensehexbytes >= 13 && lc($sensehexbytes[12]) eq "5e") {
+      warn "[DEBUG] Drive $fulldev is in SCSI low power mode\n"
+        if $DEBUG;
+      return 1;
+    }
+  }
+
+  return 0;
+}