Re: [BK PATCH] USB update for 2.6.3

David S. Miller
2004-02-20T07:04:21Z

On Thu, 19 Feb 2004 23:03:31 -0800 (PST)
Linus Torvalds <torvalds@osdl.org> wrote:

>
>
> On Fri, 20 Feb 2004, Benjamin Herrenschmidt wrote:
> >
> > > Well, we do. The pcibios_xxx routines get called for all PCI devices
> > > during discovery, and that's when you'd fill them in.
> >
> > But what about USB or FireWire devices ? In theory, I'd like to see
> > the driver for those not have to bother about beeing hosted by a PCI
> > device or whatever else (there are typically non-PCI OHCI USBs on
> > embedded platform, faking a pci_dev is becoming painful).
>
> Well, a USB device can't actually do DMA, so .. (it's only the USB _host_
> that does DMA, and while those aren't always PCI, they normally are).

You miss how all of this stuff is being used :-)

USB drivers do things like map DMA memory, and the generic DMA layer vectors it
so that if the USB device is attached to a PCI host the PCI DMA mapping routines
get used.