scan-registers: determine available notifications

00 is documented in HID++ 1.0 specification, it should be safe to set the 00
register. As another program may have written the notifications register
already and since enabling notifications has side-effects such as "disabling"
certaing functions, restore the flags after reading out available notifs.

tools/scan-registers.sh

@@ -8,15 +8,33 @@ fi
 HC="$(dirname "$(readlink -f "$0")")/hidconsole"
 
 z='0 1 2 3 4 5 6 7 8 9 a b c d e f'
+do_req() {
+	"$HC" --hidpp $2 | grep -v ' 8F.. ..0[12]' | grep -B 1 '^>> '
+}
+
+reg00=$(echo "10 0${1} 8100 000000" | do_req)
+oldflags=$(echo "$reg00" | grep -Po '>>.*? 8100 \K[0-9a-f]{6}(?=\])')
+if [ -n "$oldflags" ]; then
+	echo "# Old notification flags: $oldflags"
+	{
+		echo "10 0${1} 8000 ffffff"     # enable all notifications
+		echo "10 0${1} 8100 000000"     # read available notifs
+		echo "10 0${1} 8000 $oldflags"  # restore notifications
+	} | do_req | grep -B 1 '^>>.* 8100 '
+elif [ -n "$reg00" ]; then
+	echo "# Warning: hidconsole API got changed - unrecognized output"
+	echo "$reg00"
+fi
 
 for x in $z; do
 	for y in $z; do
+		[ "$x$y" = 00 ] || \
 		echo "10 0${1} 81${x}${y} 000000"
 	done
-done | "$HC" --hidpp $2 | grep -v ' 8F.. ..0[12]' | grep -B 1 '^>> '
+done | do_req
 
 for x in $z; do
 	for y in $z; do
 		echo "10 0${1} 83${x}${y} 000000"
 	done
-done | "$HC" --hidpp $2 | grep -v ' 8F.. ..0[12]' | grep -B 1 '^>> '
+done | do_req