module FictionalDevice
( device1
, device2
, DeviceHandle
, initDevice
, someDeviceAction
)

import Control.Concurrent
import Control.Concurrent.MVar

type BaseAddress = ...

data DeviceState = 
  DeviceState 
  { isFirstAccess :: Bool
  , baseAddress   :: BaseAddress
  , ...
  }

initialDeviceState :: BaseAddress -> DeviceState
initialDeviceState addr = DeviceState
  { isFirstAccess = True
  , baseAddress   = addr
  , ...
  }

device1baseAddresss :: BaseAddress
device1baseAddress = ...

device2baseAddresss :: BaseAddress
device2baseAddress = ...

threadlocal device1state (MVar DeviceState)
   (initTL (newMVarTL (initialDeviceState device1baseAddress)))

threadlocal device2state (MVar DeviceState)
   (initTL (newMVarTL (initialDeviceState device2baseAddress)))

newtype DeviceHandle = DH (TLRef (MVar DeviceState))

device1 = DH device1state
device2 = DH device2state

doInitDevice :: BaseAddress -> IO ()
doInitDevice addr = ...

initDevice :: DeviceHandle -> IO ()
initDevice (DH ref) = do
  stMvar <- readThreadLocal ref
  modifyMVar_ stMVar (\st -> do
    when (isFirstAccess st) (doInitDevice (baseAddress st))
    return st{ isFirstAccess = False })
  
someDeviceAction :: DeviceHandle -> IO ()
someDeviceAdction h@(DH ref) = do
  initDevice h
  ...