Re: USB and DMA on Alpha with 2.6.0-test7

[Ivan Kokshaysky]

On Fri, Oct 10, 2003 at 11:22:06AM +0200, Måns Rullgård wrote:
> Yesterday, I compiled 2.6.0-test7 for one of my Alpha boxes.  I have
> an AX8817X based USB ethernet adaptor connected to it (it's short on
> PCI slots), so I compiled the usbnet module.  When I loaded usbnet, I
> got a BUG at include/asm-generic/dma-mapping.h:19.  Apparently, DMA
> setup only works with PCI here.  How should this be fixed?  It worked
> with -test4, albeit slowly, for other reasons.

Well, the usage of dma_supported() in usbnet.c is wrong even for i386.
USB device doesn't do DMA, it's USB controller what does. The driver should
check dma_mask of the parent device instead, something like this:

	// possible with some EHCI controllers
	if (*udev->dev->parent->dma_mask == 0xffffffffffffffffULL)
		net->features |= NETIF_F_HIGHDMA;

Ivan.
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