HID functions to read back the status of an HID controller (like MIDI SYSEX)

CMakeLists.txt

@@ -2530,7 +2530,12 @@ find_package(LibUSB)
 # USB HID controller support
 find_package(hidapi)
 option(HID "USB HID controller support" ON)
-cmake_dependent_option(HIDAPI_STATIC "Link HIDAPI library statically" OFF "HIDAPI_FOUND" ON)
+
+if(hidapi_VERSION VERSION_LESS "0.10.0")
+  set(HIDAPI_STATIC ON)
+else()
+  cmake_dependent_option(HIDAPI_STATIC "Link HIDAPI library statically" OFF "HIDAPI_FOUND" ON)
+endif()
 if(HID)
   target_sources(mixxx-lib PRIVATE
     src/controllers/hid/hidcontroller.cpp

cmake/modules/Findhidapi.cmake

@@ -70,6 +70,18 @@ find_package_handle_standard_args(
   hidapi_INCLUDE_DIR
 )
 
+# Version detection
+if (EXISTS "${hidapi_INCLUDE_DIR}/hidapi.h")
+    file(READ "${hidapi_INCLUDE_DIR}/hidapi.h" hidapi_H_CONTENTS)
+    string(REGEX MATCH "#define HID_API_VERSION_MAJOR ([0-9]+)" _dummy "${hidapi_H_CONTENTS}")
+    set(hidapi_VERSION_MAJOR "${CMAKE_MATCH_1}")
+    string(REGEX MATCH "#define HID_API_VERSION_MINOR ([0-9]+)" _dummy "${hidapi_H_CONTENTS}")
+    set(hidapi_VERSION_MINOR "${CMAKE_MATCH_1}")
+    string(REGEX MATCH "#define HID_API_VERSION_PATCH ([0-9]+)" _dummy "${hidapi_H_CONTENTS}")
+    set(hidapi_VERSION_PATCH "${CMAKE_MATCH_1}")
+    set(hidapi_VERSION "${hidapi_VERSION_MAJOR}.${hidapi_VERSION_MINOR}.${hidapi_VERSION_PATCH}")
+endif ()
+
 if(hidapi_FOUND)
   set(hidapi_LIBRARIES "${hidapi_LIBRARY}")
   set(hidapi_INCLUDE_DIRS "${hidapi_INCLUDE_DIR}")

src/controllers/controller.cpp

@@ -125,7 +125,8 @@ void Controller::receive(const QByteArray& data, mixxx::Duration timestamp) {
             } else {
                 spacer = QStringLiteral(" ");
             }
-            message += QString::number(data.at(i), 16)
+            // cast to quint8 to avoid that negative chars are for instance displayed as ffffffff instead of the desired ff
+            message += QString::number(static_cast<quint8>(data.at(i)), 16)
                                .toUpper()
                                .rightJustified(2, QChar('0')) +
                     spacer;

src/controllers/hid/hidcontroller.cpp

@@ -19,7 +19,7 @@ HidController::HidController(
         mixxx::hid::DeviceInfo&& deviceInfo)
         : m_deviceInfo(std::move(deviceInfo)),
           m_pHidDevice(nullptr),
-          m_iPollingBufferIndex(0) {
+          m_pollingBufferIndex(0) {
     setDeviceCategory(mixxx::hid::DeviceCategory::guessFromDeviceInfo(m_deviceInfo));
     setDeviceName(m_deviceInfo.formatName());
 
@@ -109,7 +109,7 @@ int HidController::open() {
     for (int i = 0; i < kNumBuffers; i++) {
         memset(m_pPollData[i], 0, kBufferSize);
     }
-    m_iLastPollSize = 0;
+    m_lastPollSize = 0;
 
     setOpen(true);
     startEngine();
@@ -136,6 +136,67 @@ int HidController::close() {
     return 0;
 }
 
+void HidController::processInputReport(int bytesRead) {
+    Trace process("HidController processInputReport");
+    unsigned char* pPreviousBuffer = m_pPollData[(m_pollingBufferIndex + 1) % kNumBuffers];
+    unsigned char* pCurrentBuffer = m_pPollData[m_pollingBufferIndex];
+    // Some controllers such as the Gemini GMX continuously send input reports even if it
+    // is identical to the previous send input report. If this loop processed all those redundant
+    // input report, it would be a big performance problem to run JS code for every  input report and
+    // would be unnecessary.
+    // This assumes that the redundant input report all use the same report ID. In practice we
+    // have not encountered any controllers that send redundant input report with different report
+    // IDs. If any such devices exist, this may be changed to use a separate buffer to store
+    // the last input report for each report ID.
+    if (bytesRead == m_lastPollSize &&
+            memcmp(pCurrentBuffer, pPreviousBuffer, bytesRead) == 0) {
+        return;
+    }
+    // Cycle between buffers so the memcmp above does not require deep copying to another buffer.
+    m_pollingBufferIndex = (m_pollingBufferIndex + 1) % kNumBuffers;
+    m_lastPollSize = bytesRead;
+    auto incomingData = QByteArray::fromRawData(
+            reinterpret_cast<char*>(pCurrentBuffer), bytesRead);
+
+    // Execute callback function in JavaScript mapping
+    // and print to stdout in case of --controllerDebug
+    receive(incomingData, mixxx::Time::elapsed());
+}
+
+QList<int> HidController::getInputReport(unsigned int reportID) {
+    Trace hidRead("HidController getInputReport");
+    int bytesRead;
+
+    m_pPollData[m_pollingBufferIndex][0] = reportID;
+    bytesRead = hid_get_input_report(m_pHidDevice, m_pPollData[m_pollingBufferIndex], kBufferSize);
+
+    controllerDebug(bytesRead
+            << "bytes received by hid_get_input_report" << getName()
+            << "serial #" << m_deviceInfo.serialNumber()
+            << "(including one byte for the report ID:"
+            << QString::number(static_cast<quint8>(reportID), 16)
+                       .toUpper()
+                       .rightJustified(2, QChar('0'))
+            << ")");
+
+    if (bytesRead <= kReportIdSize) {
+        // -1 is the only error value according to hidapi documentation.
+        // Otherwise minimum possible value is 1, because 1 byte is for the reportID,
+        // the smallest report with data is therefore 2 bytes.
+        DEBUG_ASSERT(bytesRead <= kReportIdSize);
+        return QList<int>();
+    }
+
+    // Convert array of bytes read in a JavaScript compatible return type
+    // For compatibilty with the array provided by HidController::poll the reportID is contained as prefix
+    QList<int> dataList;
+    dataList.reserve(bytesRead);
+    for (int i = 0; i < bytesRead; i++) {
+        dataList.append(m_pPollData[m_pollingBufferIndex][i]);
+    }
+    return dataList;
+}
+
 bool HidController::poll() {
     Trace hidRead("HidController poll");
 
@@ -145,38 +206,16 @@ bool HidController::poll() {
     // There is no safety net for this because it has not been demonstrated to be
     // a problem in practice.
     while (true) {
-        // Cycle between buffers so the memcmp below does not require deep copying to another buffer.
-        unsigned char* pPreviousBuffer = m_pPollData[m_iPollingBufferIndex];
-        const int currentBufferIndex = (m_iPollingBufferIndex + 1) % kNumBuffers;
-        unsigned char* pCurrentBuffer = m_pPollData[currentBufferIndex];
-
-        int bytesRead = hid_read(m_pHidDevice, pCurrentBuffer, kBufferSize);
+        int bytesRead = hid_read(m_pHidDevice, m_pPollData[m_pollingBufferIndex], kBufferSize);
         if (bytesRead < 0) {
             // -1 is the only error value according to hidapi documentation.
             DEBUG_ASSERT(bytesRead == -1);
             return false;
         } else if (bytesRead == 0) {
+            // No packet was available to be read
             return true;
         }
-
-        Trace process("HidController process packet");
-        // Some controllers such as the Gemini GMX continuously send input packets even if it
-        // is identical to the previous packet. If this loop processed all those redundant
-        // packets, it would be a big performance problem to run JS code for every packet and
-        // would be unnecessary.
-        // This assumes that the redundant packets all use the same report ID. In practice we
-        // have not encountered any controllers that send redundant packets with different report
-        // IDs. If any such devices exist, this may be changed to use a separate buffer to store
-        // the last packet for each report ID.
-        if (bytesRead == m_iLastPollSize &&
-                memcmp(pCurrentBuffer, pPreviousBuffer, bytesRead) == 0) {
-            continue;
-        }
-        m_iLastPollSize = bytesRead;
-        m_iPollingBufferIndex = currentBufferIndex;
-        auto incomingData = QByteArray::fromRawData(
-                reinterpret_cast<char*>(pCurrentBuffer), bytesRead);
-        receive(incomingData, mixxx::Time::elapsed());
+        processInputReport(bytesRead);
     }
 }
 
@@ -254,3 +293,42 @@ void HidController::sendFeatureReport(
 ControllerJSProxy* HidController::jsProxy() {
     return new HidControllerJSProxy(this);
 }
+
+QList<int> HidController::getFeatureReport(
+        unsigned int reportID) {
+    unsigned char dataRead[kReportIdSize + kBufferSize];
+    dataRead[0] = reportID;
+
+    int bytesRead;
+    bytesRead = hid_get_feature_report(m_pHidDevice,
+            dataRead,
+            kReportIdSize + kBufferSize);
+    if (bytesRead <= kReportIdSize) {
+        // -1 is the only error value according to hidapi documentation.
+        // Otherwise minimum possible value is 1, because 1 byte is for the reportID,
+        // the smallest report with data is therefore 2 bytes.
+        qWarning() << "getFeatureReport is unable to get data from" << getName()
+                   << "serial #" << m_deviceInfo.serialNumber() << ":"
+                   << mixxx::convertWCStringToQString(
+                              hid_error(m_pHidDevice),
+                              kMaxHidErrorMessageSize);
+    } else {
+        controllerDebug(bytesRead
+                << "bytes received by getFeatureReport from" << getName()
+                << "serial #" << m_deviceInfo.serialNumber()
+                << "(including one byte for the report ID:"
+                << QString::number(static_cast<quint8>(reportID), 16)
+                           .toUpper()
+                           .rightJustified(2, QChar('0'))
+                << ")")
+    }
+
+    // Convert array of bytes read in a JavaScript compatible return type
+    // For compatibilty with input array HidController::sendFeatureReport, a reportID prefix is not added here
+    QList<int> dataList;
+    dataList.reserve(bytesRead - kReportIdSize);
+    for (int i = kReportIdSize; i < bytesRead; i++) {
+        dataList.append(dataRead[i]);
+    }
+    return dataList;
+}

src/controllers/hid/hidcontroller.h

@@ -40,13 +40,32 @@ class HidController final : public Controller {
 
   private:
     bool isPolling() const override;
+    void processInputReport(int bytesRead);
 
     // For devices which only support a single report, reportID must be set to
     // 0x0.
     void sendBytes(const QByteArray& data) override;
     void sendBytesReport(QByteArray data, unsigned int reportID);
     void sendFeatureReport(const QList<int>& dataList, unsigned int reportID);
 
+    // getInputReport receives an input report on request.
+    // This can be used on startup to initialize the knob positions in Mixxx
+    // to the physical position of the hardware knobs on the controller.
+    // The returned data structure for the input reports is the same
+    // as in the polling functionality (including ReportID in first byte).
+    // The returned list can be used to call the incomingData
+    // function of the common-hid-packet-parser.
+    QList<int> getInputReport(unsigned int reportID);
+
+    // getFeatureReport receives a feature reports on request.
+    // HID doesn't support polling feature reports, therefore this is the
+    // only method to get this information.
+    // Usually, single bits in a feature report need to be set without
+    // changing the other bits. The returned list matches the input
+    // format of sendFeatureReport, allowing it to be read, modified
+    // and sent it back to the controller.
+    QList<int> getFeatureReport(unsigned int reportID);
+
     const mixxx::hid::DeviceInfo m_deviceInfo;
 
     hid_device* m_pHidDevice;
@@ -55,8 +74,8 @@ class HidController final : public Controller {
     static constexpr int kNumBuffers = 2;
     static constexpr int kBufferSize = 255;
     unsigned char m_pPollData[kNumBuffers][kBufferSize];
-    int m_iLastPollSize;
-    int m_iPollingBufferIndex;
+    int m_lastPollSize;
+    int m_pollingBufferIndex;
 
     friend class HidControllerJSProxy;
 };
@@ -77,11 +96,21 @@ class HidControllerJSProxy : public ControllerJSProxy {
         m_pHidController->sendReport(data, length, reportID);
     }
 
+    Q_INVOKABLE QList<int> getInputReport(
+            unsigned int reportID) {
+        return m_pHidController->getInputReport(reportID);
+    }
+
     Q_INVOKABLE void sendFeatureReport(
             const QList<int>& dataList, unsigned int reportID) {
         m_pHidController->sendFeatureReport(dataList, reportID);
     }
 
+    Q_INVOKABLE QList<int> getFeatureReport(
+            unsigned int reportID) {
+        return m_pHidController->getFeatureReport(reportID);
+    }
+
   private:
     HidController* m_pHidController;
 };