On Fri, Dec 18, 2009 at 8:02 AM, Li Yang-R58472 [off-list ref] wrote:

quoted

Subject: Re: [PATCH v2 2/2] Crypto: Talitos: Support for
Async_tx XOR offload

Ira W. Snyder wrote:

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Yes, I have used the device_prep_dma_interrupt()

functionality quite a

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while back. However, I found it to be pretty much useless.

The specific case it is needed for Talitos/raid is a channel
switch interrupt.  The interrupt causes the cleanup operation
to be run which will kick off any pending dependent operations
on the xor channel.  In the raid case we only have callbacks
at the end of a chain, so we need the interrupt to kick the
engine in an operation chain like
xor->copy->xor->callback.

I am wondering if can use more callbacks to kick off pending dependent operations?
Like xor->callback->copy->callback->xor->callback?

No, the callback field is reserved for clients of the api.  What you want is:

xor->cleanupT->copy->cleanupF->xor->cleanupT->callback

Where cleanupT is the Talitos descriptor cleanup routine and cleanupF
is from fsldma.  The assumption is that the interrupt kicks the
cleanup routine and that calls dma_run_dependencies().

--
Dan