Re: [LKML] Re: [PATCH v3] ad7877: keep dma rx buffers in seperatecache lines

From: Nick Piggin
Date: Wed May 19 2010 - 09:52:36 EST

On Wed, May 19, 2010 at 03:44:30PM +0200, Johannes Weiner wrote:
> On Wed, May 19, 2010 at 11:36:56PM +1000, Nick Piggin wrote:
> > On Wed, May 19, 2010 at 02:17:47PM +0100, David Woodhouse wrote:
> > >
> > > The 'cacheline aligned' misconception did manage to get into the ad7877
> > > driver in commit 3843384a though -- it now uses ____cacheline_aligned
> > > instead of __attribute__((__aligned__(ARCH_KMALLOC_MINALIGN))) as it
> > > should.
> >
> > OK so long as there is not a "must be cacheline aligned" requirement.
> > Your proposal for a __dma_aligned attribute in an arch header looks
> > like a good idea there.
> Would you happen to know of other potential users? At this point I'd
> much rather just allocate the buffers dynamically and hide the issue
> nicely behind kmalloc().

I don't think we need to hide the fact that some platforms have
specific alignment restrictions for DMA. So if any drivers make use
of the alignment, I see no problem with __dma_aligned.

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at