Re: [PATCH 2/3] dma: override "dma_flags_set_dmaflush" for sn-ia64

Jes Sorensen
2007-08-22T07:41:26Z

James Bottomley wrote:
> On Tue, 2007-08-21 at 17:34 -0700, akepner@sgi.com wrote:
>> The term "posted DMA" is used to describe this behavior in the Altix
>> Device Driver Writer's Guide, but it may be confusing things here.
>> Maybe a better term will suggest itself if I can clarify....
>
> OK, but posted DMA has a pretty specific meaning in terms of PCI, hence
> the confusion.

Maybe it would be more better to refer to this as 'out of order DMA'?

>> On Altix, DMA from a device isn't guaranteed to arrive in host memory
>> in the order it was sent from the device. This reordering can happen
>> in the NUMA interconnect (it's specifically not a PCI reordering.)
>
> This is mmiowb and read_relaxed() again, isn't it?

I believe it's the same problem, except this time it's when exposing
structures to userland.

Cheers,
Jes