From: vichy > 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, The important section is 4.11.7.1, if those requirements are also met the it will go wrong in obscure ways. David ��.n��������+%������w��{.n�����{���)��jg��������ݢj����G�������j:+v���w�m������w�������h�����٥