Date: Fri, 1 Dec 2006 10:58:09 +0530 From: "Kamal R. Prasad" <kamalp@acm.org> To: freebsd-hackers@freebsd.org Subject: Re: contiguous memory allocation problem Message-ID: <ac7deb50611302128x30ed5ereaca75671117bded@mail.gmail.com> In-Reply-To: <44A87163.1020203@elischer.org> References: <200607021305.aa75873@nowhere.iedowse.com> <44A87163.1020203@elischer.org>
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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@elischer.org> wrote: > > Ian Dowse wrote: > > >In message <200607021138.11945.hselasky@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@freebsd.org mailing list > >http://lists.freebsd.org/mailman/listinfo/freebsd-hackers > >To unsubscribe, send any mail to "freebsd-hackers-unsubscribe@freebsd.org > " > > > > > _______________________________________________ > freebsd-hackers@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-hackers > To unsubscribe, send any mail to "freebsd-hackers-unsubscribe@freebsd.org" >
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