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Date: Thu, 19 Feb 2004 23:04:07 -0800
From: "David S. Miller" <davem@redhat.com>
To: Linus Torvalds <torvalds@osdl.org>
Cc: benh@kernel.crashing.org, greg@kroah.com, akpm@osdl.org,
       linux-usb-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org
Subject: Re: [BK PATCH] USB update for 2.6.3
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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.