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
