hi Mathias: > As I understood it, it is ok to cross page boundaries as long as the buffer > is physically contiguous. As our dma case should be. > xhci specification section 3.2.8 says that: > > "Note that no constraints are placed on the TRB Length fields in a > Scatter/Gather list. Classically all the > buffers pointed to by a scatter gather list were required to be “page size” > in length except for the first and > last (as illustrated by the example above). The xHCI does not require this > constraint. Any buffer pointed to > by a Normal, Data Stage, or Isoch TRB in a TD may be any size between 0 and > 64K bytes in size. For > instance, if when an OS translates a virtual memory buffer into a list of > physical pages, some of the entries > in the list reference multiple contiguous pages, the flexible Length fields > of TRBs allow a 1:1 mapping of list > entries to TRBs, i.e. a multi-page list entry does not need to be defined as > multiple page sized TRBs." > " Yes, you are correct. ^^ there is no page boundary limitation for Scatter/Gather list, but how about iso transfer? for iso TRB, it seems a limitation for not crossing page boundary in section 3.2.11.
appreciate all your kind help, -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
