contiguous memory allocation problem

[Kamal R. Prasad]

Hello,

 I would like to unsubscribe myself from all freebsd mailing lists. I have
sent an unsubscribe to freebsd-hackers-unsubscribe, but did not get any
response to verify. Since the admin is on the mailing list, I would
appreciate if you can delete my name and/or email me the procedure to
follow.

thanks
-kamal



On 7/3/06, Julian Elischer <julian at elischer.org> wrote:
>
> Ian Dowse wrote:
>
> >In message <200607021138.11945.hselasky at c2i.net>, Hans Petter Selasky
> writes:
> >
> >
> >>But there is one problem, that has been overlooked, and that is High
> speed
> >>isochronous transfers, which are not supported by the existing USB
> system. I
> >>don't think that the EHCI specification was designed for scatter and
> gather,
> >>when you consider this:
> >>
> >>8 transfers of 0xC00 bytes has to fit on 7 pages. If this is going to
> work,
> >>and I am right, one page has to contain two transfers. (see page 43 of
> >>ehci-r10.pdf)
> >>
> >>
> >
> >I haven't looked into the details, but the text in section 3.3.3
> >seems to suggest that EHCI is designed to not require physically
> >contiguous allocations here either, so the same approach of using
> >bus_dmamap_load() should work:
> >
> >  This data structure requires the associated data buffer to be
> >  contiguous (relative to virtual memory), but allows the physical
> >  memory pages to be non-contiguous. Seven page pointers are provided
> >  to support the expression of 8 isochronous transfers. The seven
> >  pointers allow for 3 (transactions) * 1024 (maximum packet size)
> >  * 8 (transaction records) (24576 bytes) to be moved with this
> >  data structure, regardless of the alignment offset of the first
> >  page.
> >
> >
>
> yes, as long as the beffers are contiguous in some virtual space then
> the maximum number of pages they
> can need is 7.
> (they actually fit into 6 but they may start part way through the first
> page and may therefore overflow into a 7th).
>
> >Ian
> >_______________________________________________
> >freebsd-hackers at freebsd.org mailing list
> >http://lists.freebsd.org/mailman/listinfo/freebsd-hackers
> >To unsubscribe, send any mail to "freebsd-hackers-unsubscribe at freebsd.org
> "
> >
> >
> _______________________________________________
> freebsd-hackers at freebsd.org mailing list
> http://lists.freebsd.org/mailman/listinfo/freebsd-hackers
> To unsubscribe, send any mail to "freebsd-hackers-unsubscribe at freebsd.org"
>