In fact, I do not have such a file. My assembly looks like this (see below). I connect the hardware component UART to the Cons_PingMe. So, I do not have any driver defined in a separate file. This is the uart_mem connection that is the issue.

I am almost sure I missed something and not sure this is a bug.

assembly.camkes:
===============
component UART{
        hardware;
        dataport Buf mem;
}


import <std_connector.camkes>;
import "components/timer/Timer.camkes";
import "components/ProducerThreadImpl/ProducerThreadImpl.camkes";
import "components/ConsumerThreadImpl/ConsumerThreadImpl.camkes";


assembly {
  composition {
        component Timerbase timerbase;
        component Timer timer;
        component UART drv;

        component ProducerThreadImpl Prod_Pinger;
        component ConsumerThreadImpl Cons_PingMe;

        connection seL4SharedData connection0(from Prod_Pinger.data_source, to Cons_PingMe.data_sink);
        connection seL4Notification notification0 (from timer.Prod_Pinger_activator, to Prod_Pinger.activator);
        connection seL4Notification notification1 (from timer.Cons_PingMe_activator, to Cons_PingMe.activator);
        connection seL4HardwareMMIO uart_mem (from drv.mem, to Cons_PingMe.mem);
        connection seL4HardwareMMIO timer_mem (from timer.reg, to timerbase.reg);
        connection seL4HardwareInterrupt timer_irq (from timerbase.irq, to timer.irq);

        }

        configuration {


connection0.from_access = "W";
connection0.to_access = "R";


timerbase.reg_attributes = "0x48040000:0x1000";
timerbase.irq_attributes = 68;       
drv.mem_attributes = "0x43F90000:0x1000";

        random.ID = 1;


    }
}

components/ConsumerThreadImpl/ConsumerThreadImpl.camkes:

====================================================
component ConsumerThreadImpl
{
        include "generatedtypes.h";
        control;
        dataport simpletype data_sink;
        consumes sig activator;
        dataport Buf mem;
}