Re: [PATCH 0/3] fix GART to respect device's dma_mask aboutvirtual mappings

[FUJITA Tomonori]

On Mon, 22 Sep 2008 22:35:18 +0200
Andi Kleen <andi@xxxxxxxxxxxxxx> wrote:

> On Tue, Sep 23, 2008 at 04:12:33AM +0900, FUJITA Tomonori wrote:
> > Sure, pci-nommu's map_sg/map_single doesn't handle it. But we handle
> > this issue somewhere else (like b44 keeps own DMA buffer)?
> 
> Yes, b44 handles it on its own. It has to for 32bit which always
> has a nop map_sg/single. Also some other subsystems like the block layer
> do it implicitely.

Yeah, 'somewhere else' includes the block layer bounce.


> > 1. not all map_sg/map_single (e.g. pci-nommu) can't handle it.
> 
> and especially i386
> 
> > 2. we already have workarounds for it somewhere else so
> > map_sg/map_single don't need to handle it.
> > 3. I changed GART map_sg/map_signle to handle it. I thought if it
> > can handle it, for example, b44 doesn't go the workaround path. It
> > would be a good thing.
> > 4. But GART cannot remap to addresses < 4GB reliably, so my above
> > argument doesn't always work.
> > 5. Then my patch doesn't break anything but it's almost meaningless.
> 
> Correct.

Thanks for the clarification.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/