InputDevice: return std::optional from getAbsoluteAxisInfo

This also allows us to remove the valid field from RawAbsoluteAxisInfo,
since we can represent "invalid" axes (which usually just meant absent
ones) using std::nullopt.

Test: atest inputflinger_tests
Test: m checkinput
Test: Check "Raw Touch Axes" section of touch input mapper info in
      dumpsys input
Bug: 245989146
Flag: EXEMPT refactor
Change-Id: I045a2e0b61a84657f2f8171c1fee3cc3e331ac86
diff --git a/services/inputflinger/reader/mapper/TouchpadInputMapper.cpp b/services/inputflinger/reader/mapper/TouchpadInputMapper.cpp
index 24efae8..daab636 100644
--- a/services/inputflinger/reader/mapper/TouchpadInputMapper.cpp
+++ b/services/inputflinger/reader/mapper/TouchpadInputMapper.cpp
@@ -240,14 +240,15 @@
         mGestureConverter(*getContext(), deviceContext, getDeviceId()),
         mCapturedEventConverter(*getContext(), deviceContext, mMotionAccumulator, getDeviceId()),
         mMetricsId(metricsIdFromInputDeviceIdentifier(deviceContext.getDeviceIdentifier())) {
-    RawAbsoluteAxisInfo slotAxisInfo;
-    deviceContext.getAbsoluteAxisInfo(ABS_MT_SLOT, &slotAxisInfo);
-    if (!slotAxisInfo.valid || slotAxisInfo.maxValue < 0) {
+    if (std::optional<RawAbsoluteAxisInfo> slotAxis =
+                deviceContext.getAbsoluteAxisInfo(ABS_MT_SLOT);
+        slotAxis && slotAxis->maxValue >= 0) {
+        mMotionAccumulator.configure(deviceContext, slotAxis->maxValue + 1, true);
+    } else {
         LOG(WARNING) << "Touchpad " << deviceContext.getName()
                      << " doesn't have a valid ABS_MT_SLOT axis, and probably won't work properly.";
-        slotAxisInfo.maxValue = 0;
+        mMotionAccumulator.configure(deviceContext, 1, true);
     }
-    mMotionAccumulator.configure(deviceContext, slotAxisInfo.maxValue + 1, true);
 
     mGestureInterpreter->Initialize(GESTURES_DEVCLASS_TOUCHPAD);
     mGestureInterpreter->SetHardwareProperties(createHardwareProperties(deviceContext));