Messages in this thread | | | Date | Wed, 2 Jan 2002 23:32:45 +0100 (MET) | From | <> | Subject | Re: [linux-usb-devel] Re: highmem and usb [was "sr: unalignedtransfer" in 2.5.2-pre1] |
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On Wed, 2 Jan 2002, Jens Axboe wrote:
> 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.
Probably for a long time they'll be the only ones. All the char drivers will mainly do a copy_to/from_user or want memory they can manipulate directly.
Regards Oliver
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