Now I'm not following _you_ ... could you give an example of
what you mean?
In my proposal, device drivers would be able to either use
the current rules (which they do already, so no problem :)
OR (new) specify highmem buffers by {page+offset, length}.
At what point does a driver need to know what kind of memory
to allocate? Near as I can figure, the only question is what type
was passed (answered by the original proposal) and then other
issues are all resolved by using appropriate PCI mapping calls.
- Dave
----- Original Message -----
From: <[EMAIL PROTECTED]>
To: "David Brownell" <[EMAIL PROTECTED]>
Cc: <[EMAIL PROTECTED]>
Sent: Thursday, January 03, 2002 4:22 AM
Subject: Re: [linux-usb-devel] Re: highmem and
usb[was:"sr:unalignedtransfer"in2.5.2-pre1]
> > > > > 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 of 32bit OHCI and 64bit EHCI ?
> >
> > It's all done through pci_set_dma_mask() ... by default, the mask is
> > set for 32bit DMA. And whatever it is, the PCI layer deals with it
> > transparently when it sets up DMA mappings.
>
> Still, I don't see it. We still want to allocate the right kind of memory
> in the drivers and we need to export this information from the hcd level
> somehow.
>
> Regards
> Oliver
>
>
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