> > A driver on a 64bit system with a 32bit host controller, if the system
> > has more than 4GB of RAM.
>
> By the time such systems become problematic, I'd expect hardware
> vendors would be phasing out such 32bit I/O controllers. Remember
> they're mostly integrated on motherboards.
You are r
> > Now I'm not following _you_ ... could you give an example of
> > what you mean?
>
> A driver on a 64bit system with a 32bit host controller, if the system
> has more than 4GB of RAM.
By the time such systems become problematic, I'd expect hardware
vendors would be phasing out such 32bit I/O
> > > > On 64Bit machines we might have to deal with HCDs who can do 32Bit DMA
> > > > only. Perhaps there should be a gfp field in the usb_device struct
> > > > to export knowledge about the memory the HCD can cope with.
> > >
> > > Shouldn't be needed.
> >
> > How do we deal with the combination
> > > > > I presume there is some overhead in bouncing to lowmem? I imagine that
> > > > > highmem support for the HCDs wouldn't be that difficult -- they are just
> > > > > PCI devices, after all.
> > > >
> > > > I'm unclear on what "bouncing to lowmem" involves, but I'd rather avoid
> > > > tea
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,
On Wed, 2 Jan 2002, David Brownell wrote:
> > > > I presume there is some overhead in bouncing to lowmem? I imagine that
> > > > highmem support for the HCDs wouldn't be that difficult -- they are just
> > > > PCI devices, after all.
> > >
> > > I'm unclear on what "bouncing to lowmem" involves,
On Wed, Jan 02 2002, David Brownell wrote:
> > > 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 "transf
> > 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
>
> > > I'd rather eliminate as much overhead as possible -- I already get
> > > complaints from performance fanatics about the inability of usb-storage to
> > > get past 92% bus saturation (sustained), and the problem will only get
> > > worse on USB 2.0
> >
> > Well then you'll be glad to see a p
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 creat
> > 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
On Tue, Jan 01 2002, David Brownell wrote:
> > > Not that I've seen a writeup about highmem (linux/Documentation
> > > doesn't seem to have one anyway) but if I infer correctly from that
> > > DMA-mapping.txt writeup, URBs don't support it because there's no way
> > > to specify buffers as a "stru
On Tue, Jan 01 2002, David Brownell wrote:
> > > No, you can always ask to get pages low mem bounced. Highmem is no
> > > requirement, and if your device really can't support it there's no point
> > > in attempting to support it.
> >
> > I presume there is some overhead in bouncing to lowmem? I i
> > I presume there is some overhead in bouncing to lowmem? I imagine that
> > highmem support for the HCDs wouldn't be that difficult -- they are just
> > PCI devices, after all.
>
> I'm unclear on what "bouncing to lowmem" involves, but I'd rather avoid
> teaching all three HCDs a second model
> > > Not that I've seen a writeup about highmem (linux/Documentation
> > > doesn't seem to have one anyway) but if I infer correctly from that
> > > DMA-mapping.txt writeup, URBs don't support it because there's no way
> > > to specify buffers as a "struct page *" or an array of "struct
> > > sca
> > Not that I've seen a writeup about highmem (linux/Documentation
> > doesn't seem to have one anyway) but if I infer correctly from that
> > DMA-mapping.txt writeup, URBs don't support it because there's no way
> > to specify buffers as a "struct page *" or an array of "struct
> > scatterlist".
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