> Anyway, what my driver does is to issue these control
> requests (usbd_do_request()) within a callout(9)
> handler, and to stuff the result into a tty.
> 
> Now I'm getting a kernel diagnostic warning from tome to time:
> WARNING: WANT PMAPLOAD ON SYSCALL ENTRY

it usually means context switch in illegal context.
i guess usbd_do_request can't be used from interrupt context.

YAMAMOTO Takashi