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[High] refill work racing mhi_unprepare_from_transfer() in remove(): agreed, and Loic raised the same point. In v9 the DL sink buffer is only requeued from the refill work (the DL callback just schedules it), and remove() calls disable_delayed_work_sync() before mhi_unprepare_from_transfer(), the same order mhi_wwan_ctrl_stop() uses for the data ports. [Medium] a DL callback still running after remove() frees dtr: v9's change stops a late callback from re-arming the work, but if a callback could still be running after mhi_unprepare_from_transfer() returns, it would also touch freed memory. That is the same guarantee the existing data-port code in this driver relies on, as mhi_wwan_ctrl_remove() frees mhiwwan after the channel is unprepared while mhi_dl_xfer_cb() dereferences it. So if the window you describe can happen, I think it belongs in the MHI core rather than in each client driver, and I've left this driver consistent with the rest. [Medium] DTR/RTS updates that don't reach the modem are not retried or replayed: this is intended and described in the commit message. Each TIOCMSET/TIOCMBIS/TIOCMBIC resends the full state, open and close send it again, and cdc-acm treats a failed control request the same way. The replay case needs the IP_CTRL device to be unbound and rebound by hand while an AT port is open. v9 follows with these changes.