Re: DMA APIs gumble grumble

[David Miller <davem@davemloft.net>]

From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Date: Wed, 08 Nov 2006 16:23:40 +1100

> Then, maybe 6 month, maybe 1 year later, we can change archs that use
> the "alternate" semantic like sparc64 to no longer fail
> pci_set_dma_mask(64bits).
> 
> In fact, the only breakage here would be for those archs to have some
> drivers start going slowly, though we could expect drivers to have been
> fixed by then.... (And we can delay that second part of the change as
> long as deemed necessary).

The arch implementations of pci_map_*() et al. might start
failing since they were written assuming that DAC never got
enabled.

> Yup, but you didn't fix sparc32 :-) I suppose I can try to do it and ask
> Anton for help if things go wrong, though I can't be bothered building a
> cross toolchain or getting a box on ebay so I'll rely on your for
> testing :-)

I only do sparc32 build testing, which you can do on a sparc64
box and Al Viro has great recipies for cross tool building and
usage.

> Thus, that is 3 pointers gone for archs who don't use these, and the ability
> to put things like your dma ops in every struct device.

How exactly does your device struct extension work?  I ask because
struct device is embedded into other structs, such as pci_dev,
so it has to be fixed in size unless you have some clever trick. :)