Re: [linux-usb-devel] Re: highmem and usb [was: "sr: unaligned transfer" in 2.5.2-pre1]

From: Jens Axboe (
Date: Wed Jan 02 2002 - 04:31:14 EST

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 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 for addressing transfer buffers.
> At least until later in the 2.5 series, when we believe they'll share a lot
> more common code and so that new model can be taught to just ONE
> piece of code. Fixing bugs in one place easier than in three!

Ehm I was discussing 2.5, 2.4 will always bounce the high mem pages for
you so it's moot there.

Jens Axboe

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