Re: MAX_DMA_ADDRESS, virt_to_bus (and 3c505.c bug)

Alan Cox (alan@lxorguk.ukuu.org.uk)
Fri, 6 Nov 1998 14:22:40 +0000 (GMT)

> if (virt_to_bus(skb->data) < MAX_DMA_ADDRESS) {
> memcpy(device->bouncebuf, skb->data, skb->len);
> device->txbuf = device->bouncebuf;
> } else
> device->txbuf = skb->data;
>
> This does not work, because the MAX_DMA_ADDRESS is #defined to be
> PAGE_OFFSET+0x01000000, so it refers to the _virtual_ address instead of
> the bus one. The correct condition should be

It also has another error.
>
> if (skb->data < MAX_DMA_ADDRESS) ...

Nope

(skb->data+skb->len)

and you ought to check it doesnt span a page. The 85230 driver has the
right bits in for that now. I've never seen a frame spanning a 64K boundary
on x86, and the mm may actually mean it cant occur.

Alan

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