Messages in this thread | | | Subject | Re: [PATCH] dmaengine: clean up and abstract function types (was Re: [PATCH 08/19] dmaengine: enable multiple clients and operations) | From | Alan Cox <> | Date | Tue, 19 Sep 2006 12:20:09 +0100 |
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Ar Llu, 2006-09-18 am 20:05 -0500, ysgrifennodd Olof Johansson: > On Mon, 18 Sep 2006 15:56:37 -0700 "Dan Williams" <dan.j.williams@gmail.com> wrote:
> op.src_type = PG; op.src = pg; > op.dest_type = BUF; op.dest = buf; > op.len = len; > dma_async_commit(chan, op);
At OLS Linus suggested it should distinguish between sync and async events for locking reasons.
if(dma_async_commit(foo) == SYNC_COMPLETE) { finalise_stuff(); }
else /* will call foo->callback(foo->dev_id) */
because otherwise you have locking complexities - the callback wants to take locks to guard the object it works on but if it is called synchronously - eg if hardware is busy and we fall back - it might deadlock with the caller of dmaa_async_foo() who also needs to hold the lock.
Alan
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