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
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