Messages in this thread | | | Date | Wed, 2 Jan 2002 19:44:04 +0100 | From | Jens Axboe <> | Subject | Re: [linux-usb-devel] Re: highmem and usb [was "sr: unaligned transfer" in 2.5.2-pre1] |
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On Wed, Jan 02 2002, David Brownell wrote: > > > requirement for drivers is that the transfer buffers can be passed to > > > pci_map_single() calls by the Host Controller Drivers (HCDs). The > > > device drivers, and URBs, don't expose such mappings, they only > > > require that they can be created/destroyed. > > > > .. which is the requirement that you want to change to use pci_map_page > > or pci_map_sg > > OK, I think I'm clear on this much then: in 2.5, to support block drivers > over USB (usb-storage only, for now) there needs to be an addition to > the buffer addressing model in usbcore, as exposed by URBs. > > - Current "transfer_buffer" + "transfer_buffer_length" mode needs to > stay, since most drivers aren't block drivers.
Why? Surely USB block drivers are not the only ones that want to support highmem.
> - Add some kind of "page + offset" addressing model.
Yes
> Discussion of details can be taken off LKML, it'd seem. Though I'm > curious when the scatterlist->address field will vanish, making these > changes a requirement. Is that a 2.5.2 thing?
Maybe 2.5.3, dunno for sure.
> Also, I noticed that include/asm-sparc/pci.h doesn't include the > standard pci_map_page() call ... what's up with that? That surely > causes portability problems.
It probably isn't up to snuff yet.
-- Jens Axboe
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