This all goes through the PCI DMA API anyway, which IIRC, makes the appropriate guarantees.
JE On Sat, Nov 10, 2001, David Brownell <[EMAIL PROTECTED]> wrote: > That one's already handled by the generic "transfer buffers > must be DMA-able" requirement. Allocate with kmalloc > (or what it uses internally) and you're safe. Taking memory > from a user mode buffer and playing memory mapping > tricks ... be careful and it's probably still doable. But zero > copy USB I/O probably won't be valuable till more folk > are using USB 2.0 devices ... :) > > - Dave > > ----- Original Message ----- > From: "John S. Howard" <[EMAIL PROTECTED]> > To: <[EMAIL PROTECTED]> > Sent: Saturday, November 10, 2001 12:18 PM > Subject: Re: [linux-usb-devel] uchi lockup > > > > y'all probably already know this, but uhci TDs require contiguous memory for > > the entire transaction. if your packet buffer spans a page boundary, the > > next page must be contiguous. > > > > Regards > > > > John H. > > > > > > > > Ought to be fine, so long as the controller does DMA right, > > > unless the UHCI spec demands otherwise. > > > > > > Most of the host controllers only demand alignment for their > > > control infrastructure (QH, TD/ED, etc) so far as I've seen. > > > I think the expectation is that device drivers are better off > > > not having to copy transfer buffers to force alighment. > > > > > > - Dave > > > > > > > > > ----- Original Message ----- > > > From: "Johannes Erdfelt" <[EMAIL PROTECTED]> > > > To: <[EMAIL PROTECTED]> > > > Sent: Wednesday, November 07, 2001 5:33 PM > > > Subject: Re: [linux-usb-devel] uchi lockup > > > > > > > > > > On Wed, Nov 07, 2001, Matthew Dharm > > > <[EMAIL PROTECTED]> wrote: > > > > > Interesting... off the cuff, does uhci.o have any known > > > problems with > > > > > misaligned buffers? > > > > > > > > None that I know of. > > > > > > > > IIRC, the UHCI spec allows transfers from misaligned > > > buffers. However, > > > > we go through a layer of indirection with the PCI DMA API. > > > I wonder if > > > > it's safe. > > > > > > > > JE > > > > > > > > > > _______________________________________________ > > [EMAIL PROTECTED] > > To unsubscribe, use the last form field at: > > https://lists.sourceforge.net/lists/listinfo/linux-usb-devel > > > _______________________________________________ > [EMAIL PROTECTED] > To unsubscribe, use the last form field at: > https://lists.sourceforge.net/lists/listinfo/linux-usb-devel _______________________________________________ [EMAIL PROTECTED] To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
