Re: [Qemu-devel] [PATCH] dma: Define dma_context_memory and use in sysbus-ohci

[Peter Maydell]

On 26 October 2012 14:09, Paolo Bonzini <address@hidden> wrote:
> As soon as Avi's iommu patches go in, in fact, dma->as will just be as.
> Even if as == NULL were to be outlawed and you'd be forced to write
> get_address_space_memory(), taking the pain to create dummy DMAContexts
> now is just not worth it.

Personally I think it's better not to permit NULL DMAContexts or
AddressSpaces here, because they're kind of a hack (in the same way
that the "system address space" is kind of a hack). In real hardware
you probably aren't really doing dma to that address space but to
some more local bus. dma_context_memory/address_space_memory are
nice and easy to search for, whereas NULL isn't. [And in general
I think NULL is too easy to use; if you have to go looking for the
system dma context you've been prompted to think about whether
that's the right one...]

-- PMM