[PATCH 1/2] ARM: convert dma-mapping to asm-generic API

On Tue, Dec 21, 2010 at 10:36:52AM +0000, Russell King - ARM Linux wrote:

On Tue, Dec 21, 2010 at 10:20:01AM +0000, Jamie Iles wrote:

quoted

Note: this patch also requires "ARM: dmabounce: fix partial sync in
dma_sync_single_* API" from FUJITA Tomonori:

	http://www.spinics.net/lists/netdev/msg126826.html

which allows us to do fuzzy matching of the buffers when using
dmabounce.

Which I've already said no to.

Ok, perhaps I missed some other posts. From that thread the only objections I 
found were to do with the indentation style and they were fixed up.

I don't believe that the direction taken there is anywhere near the right
one - the approach we have (implementing the whole buffer sync in terms
of the partial buffer sync) is the far more logical, simpler and safer
way, and doesn't lead to the possibility of two partially overlapping
mappings causing the wrong one to be operated upon.

The debug code doesn't check for overlapping mappings in any way, so we
can't say that they never occur.

With the way that the DMA API has gone, I view the "generic" stuff as
a disaster.

Ok I can't disagree with that. I've had a look at some of the other arches and 
I can't see an obvious reason why we couldn't change the generic 
implementation to do the sync in the way you describe. Perhaps I'll have a 
look at that after the holidays.

With regards to the API debug, any objections to adding the necessary calls 
into the existing ARM implementation? Perhaps it'll catch some misuses of the 
API.

Jamie