Re: USB and DMA on Alpha with 2.6.0-test7

From: Måns Rullgård
Date: Fri Oct 10 2003 - 06:40:05 EST

Ivan Kokshaysky <ink@xxxxxxxxxxxxxxxxxxxx> writes:

> > 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

That's what I thought.

> 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;

Is that all there is to it?

Måns Rullgård
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