How to detect MTP slave mode on Android

Question

I am trying to detect when an android device is in MTP slave mode (It is being read from).

I have a service and I can poll if need be.

I have tried broadcast receiver for USB connect and disconnect.

IntentFilter filter = new IntentFilter();
        filter.addAction(UsbManager.ACTION_USB_DEVICE_DETACHED);
        filter.addAction(UsbManager.ACTION_USB_DEVICE_ATTACHED);
        registerReceiver(mUsbReceiver, filter);

I tried USB state receiver:

        Intent intent = m_ctx.registerReceiver(null, new IntentFilter("android.hardware.usb.action.USB_STATE"));
        if (intent.getExtras().getBoolean("connected")){
            return "connected";
        } else {
            return "not-connected";
        }

This worked on my test device, but this code is running on a proprietary ROM and this intent causes device to freeze.

I have tried scraping lsusb and cat /sys/bus/usb/devices/*/product. However neither of these show any connections when the device is slave and not host.

I need to detect when a device has attached and MTP has started.

Is there a service or android daemon that activates for mtp connection I can poll to see if active?

I need anyway to detect. Root is available.