Just to clear up a small disagreement... On Fri, 20 Feb 2004, Linus Torvalds wrote:
> On Thu, 19 Feb 2004, David S. Miller wrote: > > On Fri, 20 Feb 2004 18:10:41 +1100 > > Benjamin Herrenschmidt <[EMAIL PROTECTED]> wrote: > > > > > Hrm... so if the USB device drivers are actually doing the dma mapping > > > themselves, it make sense for them to pass their own struct device, no ? > > > > That's right, at least that was the idea. > > No. That would be _fundamentally_ wrong. > > There's no way a USB device can do DMA in the first place. It has no DMA > controller, and no way to read/write memory except through the USB host. > > So it is the host - and only the host - that matters. Anything else is a > bug. Both of you are right. Linus is right that USB devices don't do DMA. Ben is right that sometimes a USB device _driver_ will set up a DMA mapping. And of course, it is set up on behalf of the corresponding USB controller, so the controller's struct device would be passed. Alan Stern ------------------------------------------------------- SF.Net is sponsored by: Speed Start Your Linux Apps Now. Build and deploy apps & Web services for Linux with a free DVD software kit from IBM. Click Now! http://ads.osdn.com/?ad_id=1356&alloc_id=3438&op=click _______________________________________________ [EMAIL PROTECTED] To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
