Re: PCI DMA to small buffers on cache-incoherent arch

William Jhun
2002-06-12T16:09:18Z

On Wed, Jun 12, 2002 at 04:47:59AM -0700, David S. Miller wrote:
> From: William Jhun <wjhun@ayrnetworks.com>
> Date: Mon, 10 Jun 2002 11:07:40 -0700
>
> On Sun, Jun 09, 2002 at 09:27:05PM -0700, David S. Miller wrote:
> > I'm trying to specify this such that knowledge of cachelines and
> > whatnot don't escape the arch specific code, ho hum... Looks like
> > that isn't possible.
>
> Perhaps provide macros in asm/pci.h that will:
>
> You don't understand, I think. I want to avoid the drivers doing
> any of the "align this, align that" stuff. I want the allocation
> to do it for them, that way the code is in one place.

No, I do understand your point. And this does not bring "knowledge of
cachelines and whatnot" into the driver; those "macros" could similarly
be calls to arch-specific code that acts based on a pdev. I was simply
trying to think of a compromise between that and massively changing the
interface by which a driver obtains buffers. And I assume alloc_skb()
and others would need to change otherwise. How would you specify if your
skb data needs to be PCI DMA-able? What about net drivers not using DMA
at all?

Thanks,
Will