Messages in this thread | ![/](/images/icornerl.gif) | | Subject | Re: [RFC] dma: passing "attributes" to dma_map_* routines | From | Benjamin Herrenschmidt <> | Date | Sat, 22 Dec 2007 08:31:30 +1100 |
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On Fri, 2007-12-21 at 10:00 -0800, akepner@sgi.com wrote: > On Fri, Dec 21, 2007 at 07:56:25AM +1100, Benjamin Herrenschmidt wrote: > > ... > > Can't you just have a primitive to sync things up that you call > > explicitely from your driver after fetching a new status entry ? > > > > Well, the only mechanisms I know to get things synced are the ones > I mentioned before: 1) generate an interrupt, 2) write to memory > which has the "barrier" attribute. Obviously 1 is out - giving > the memory used for status indications the barrier attribute is > the most primitive means I'm aware of.
Well, I'm not totally against turning "direction" into a flag mask, as I do have requests to do something similar on some PowerPC's in fact in order to control the ordering guarantees of a given DMA mapping (ie. relaxed vs. fully ordered).
I'm just worried that we'll end up with as many semantics for those flags as we have host bridges & archs around, which would be bad.
Ben.
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