fix error message when no raw device found

src/simple-mtpfs-fuse.h

@@ -72,7 +72,7 @@ public:
     bool parseOptions(int argc, char **argv);
     void printHelp() const;
     void printVersion() const;
-    void listDevices() { m_device.listDevices(); }
+    bool listDevices() { return m_device.listDevices(); }
 
     bool exec();
     bool isGood() const { return m_options.m_good; }

src/simple-mtpfs-main.cpp

@@ -39,10 +39,8 @@ int main(int argc, char **argv)
         return 0;
     }
 
-    if (filesystem->isListDevices()) {
-        filesystem->listDevices();
-        return 0;
-    }
+    if (filesystem->isListDevices())
+        return !filesystem->listDevices();
 
     return !filesystem->exec();
 }

src/simple-mtpfs-mtp-device.cpp

@@ -107,19 +107,23 @@ void MTPDevice::disconnect()
     logmsg("Disconnected.\n");
 }
 
-void MTPDevice::listDevices()
+bool MTPDevice::listDevices()
 {
     int raw_devices_cnt;
     LIBMTP_raw_device_t *raw_devices;
     LIBMTP_error_number_t err = LIBMTP_Detect_Raw_Devices(
         &raw_devices, &raw_devices_cnt);
-    if (err != 0)
-        return;
+    if (err != 0) {
+        if (err == LIBMTP_ERROR_NO_DEVICE_ATTACHED)
+            std::cerr << "No raw devices found.\n";
+        return false;
+    }
 
     for (int i = 0; i < raw_devices_cnt; ++i) {
         std::cout << i + 1 << ": " << raw_devices[i].device_entry.vendor
             << raw_devices[i].device_entry.product << "\n";
     }
+    return true;
 }
 
 uint64_t MTPDevice::storageTotalSize() const

src/simple-mtpfs-mtp-device.h

@@ -37,7 +37,7 @@ public:
     bool connect(int dev_no = 0);
     void disconnect();
 
-    void listDevices();
+    bool listDevices();
     void enableMove(bool e = true) { m_move_enabled = e; }
 
     uint64_t storageTotalSize() const;