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and specify that usb_dma attribute to dev/usb/usb_mem.c. usb_mem.c uses bus_dma(9) for DMA memory allocation, but non-DMA capable USB host controllers like slhci(4) doesn't need them at all, and some ports don't bother to prepare MD bus_dma(9) implementation (yet). Discussed on current-users http://mail-index.NetBSD.org/current-users/2011/03/13/msg015995.html and usb_dma attribute is suggested by bouyer@. Tested by kiyohara@ on mmeye with slhci at pcmcia.