diff --git a/include/boo/inputdev/DeviceBase.hpp b/include/boo/inputdev/DeviceBase.hpp
index 2e7751e..4de7b5b 100644
--- a/include/boo/inputdev/DeviceBase.hpp
+++ b/include/boo/inputdev/DeviceBase.hpp
@@ -54,18 +54,18 @@ public:
   bool sendUSBInterruptTransfer(const uint8_t* data, size_t length);
   size_t receiveUSBInterruptTransfer(uint8_t* data, size_t length);
 
-  inline unsigned getVendorId();
-  inline unsigned getProductId();
-  inline std::string_view getVendorName();
-  inline std::string_view getProductName();
+  inline unsigned getVendorId() const;
+  inline unsigned getProductId() const;
+  inline std::string_view getVendorName() const;
+  inline std::string_view getProductName() const;
 
   /* High-Level API */
 #if _WIN32
 #if !WINDOWS_STORE
-  const PHIDP_PREPARSED_DATA getReportDescriptor();
+  PHIDP_PREPARSED_DATA getReportDescriptor() const;
 #endif
 #else
-  std::vector<uint8_t> getReportDescriptor();
+  std::vector<uint8_t> getReportDescriptor() const;
 #endif
   bool sendHIDReport(const uint8_t* data, size_t length, HIDReportType tp, uint32_t message = 0);
   size_t receiveHIDReport(uint8_t* data, size_t length, HIDReportType tp,
diff --git a/include/boo/inputdev/DeviceFinder.hpp b/include/boo/inputdev/DeviceFinder.hpp
index c3b633d..3acb551 100644
--- a/include/boo/inputdev/DeviceFinder.hpp
+++ b/include/boo/inputdev/DeviceFinder.hpp
@@ -41,11 +41,8 @@ private:
 
   /* Friend methods for platform-listener to find/insert/remove
    * tokens with type-filtering */
-  bool _hasToken(const std::string& path) {
-    auto preCheck = m_tokens.find(path);
-    if (preCheck != m_tokens.end())
-      return true;
-    return false;
+  bool _hasToken(const std::string& path) const {
+    return m_tokens.find(path) != m_tokens.end();
   }
   bool _insertToken(std::unique_ptr<DeviceToken>&& token) {
     if (DeviceSignature::DeviceMatchToken(*token, m_types)) {
@@ -77,8 +74,12 @@ public:
   public:
     CDeviceTokensHandle(DeviceFinder& finder) : m_finder(finder) { m_finder.m_tokensLock.lock(); }
     ~CDeviceTokensHandle() { m_finder.m_tokensLock.unlock(); }
-    TDeviceTokens::iterator begin() { return m_finder.m_tokens.begin(); }
-    TDeviceTokens::iterator end() { return m_finder.m_tokens.end(); }
+
+    TDeviceTokens::iterator begin() noexcept { return m_finder.m_tokens.begin(); }
+    TDeviceTokens::iterator end() noexcept { return m_finder.m_tokens.end(); }
+
+    TDeviceTokens::const_iterator begin() const noexcept { return m_finder.m_tokens.begin(); }
+    TDeviceTokens::const_iterator end() const noexcept { return m_finder.m_tokens.end(); }
   };
 
   /* Application must specify its interested device-types */
diff --git a/include/boo/inputdev/DualshockPad.hpp b/include/boo/inputdev/DualshockPad.hpp
index a98f6cb..b8b2ed4 100644
--- a/include/boo/inputdev/DualshockPad.hpp
+++ b/include/boo/inputdev/DualshockPad.hpp
@@ -136,7 +136,7 @@ public:
 
   void stopRumble(int motor) { m_rumbleRequest &= ~EDualshockMotor(motor); }
 
-  EDualshockLED getLED() { return m_led; }
+  EDualshockLED getLED() const { return m_led; }
 
   void setLED(EDualshockLED led, bool on = true) {
     if (on)
diff --git a/include/boo/inputdev/NintendoPowerA.hpp b/include/boo/inputdev/NintendoPowerA.hpp
index ac9f375..20096a1 100644
--- a/include/boo/inputdev/NintendoPowerA.hpp
+++ b/include/boo/inputdev/NintendoPowerA.hpp
@@ -23,8 +23,8 @@ struct NintendoPowerAState {
   uint8_t leftY;
   uint8_t rightX;
   uint8_t rightY;
-  bool operator==(const NintendoPowerAState& other);
-  bool operator!=(const NintendoPowerAState& other);
+  bool operator==(const NintendoPowerAState& other) const;
+  bool operator!=(const NintendoPowerAState& other) const;
 };
 
 class NintendoPowerA;
diff --git a/lib/graphicsdev/Common.hpp b/lib/graphicsdev/Common.hpp
index 8471216..2fe8c93 100644
--- a/lib/graphicsdev/Common.hpp
+++ b/lib/graphicsdev/Common.hpp
@@ -249,7 +249,7 @@ public:
     m_backcv.wait(lk, [this]() { return m_outstandingTasks == 0 || !m_running; });
   }
 
-  bool isReady() {
+  bool isReady() const {
     return m_outstandingTasks == 0 || !m_running;
   }
 
diff --git a/lib/inputdev/DeviceBase.cpp b/lib/inputdev/DeviceBase.cpp
index 01fe6da..29d4412 100644
--- a/lib/inputdev/DeviceBase.cpp
+++ b/lib/inputdev/DeviceBase.cpp
@@ -37,25 +37,25 @@ size_t DeviceBase::receiveUSBInterruptTransfer(uint8_t* data, size_t length) {
   return false;
 }
 
-unsigned DeviceBase::getVendorId() {
+unsigned DeviceBase::getVendorId() const {
   if (m_token)
     return m_token->getVendorId();
   return -1;
 }
 
-unsigned DeviceBase::getProductId() {
+unsigned DeviceBase::getProductId() const {
   if (m_token)
     return m_token->getProductId();
   return -1;
 }
 
-std::string_view DeviceBase::getVendorName() {
+std::string_view DeviceBase::getVendorName() const {
   if (m_token)
     return m_token->getVendorName();
   return {};
 }
 
-std::string_view DeviceBase::getProductName() {
+std::string_view DeviceBase::getProductName() const {
   if (m_token)
     return m_token->getProductName();
   return {};
@@ -63,14 +63,14 @@ std::string_view DeviceBase::getProductName() {
 
 #if _WIN32
 #if !WINDOWS_STORE
-const PHIDP_PREPARSED_DATA DeviceBase::getReportDescriptor() {
+PHIDP_PREPARSED_DATA DeviceBase::getReportDescriptor() const {
   if (m_hidDev)
     return m_hidDev->_getReportDescriptor();
   return {};
 }
 #endif
 #else
-std::vector<uint8_t> DeviceBase::getReportDescriptor() {
+std::vector<uint8_t> DeviceBase::getReportDescriptor() const {
   if (m_hidDev)
     return m_hidDev->_getReportDescriptor();
   return {};
diff --git a/lib/inputdev/NintendoPowerA.cpp b/lib/inputdev/NintendoPowerA.cpp
index 8a31d2d..0c1e944 100644
--- a/lib/inputdev/NintendoPowerA.cpp
+++ b/lib/inputdev/NintendoPowerA.cpp
@@ -33,12 +33,10 @@ void NintendoPowerA::finalCycle() {}
 
 void NintendoPowerA::receivedHIDReport(const uint8_t* data, size_t length, HIDReportType tp, uint32_t message) {}
 
-bool NintendoPowerAState::operator==(const NintendoPowerAState& other) {
-  return !memcmp(this, &other, sizeof(NintendoPowerAState));
+bool NintendoPowerAState::operator==(const NintendoPowerAState& other) const {
+  return memcmp(this, &other, sizeof(NintendoPowerAState)) == 0;
 }
 
-bool NintendoPowerAState::operator!=(const NintendoPowerAState& other) {
-  return memcmp(this, &other, sizeof(NintendoPowerAState));
-}
+bool NintendoPowerAState::operator!=(const NintendoPowerAState& other) const { return !operator==(other); }
 
 } // namespace boo