Messages in this thread |  | | Date | Tue, 28 Mar 2006 10:44:00 -0800 | From | "Andrew Grover" <> | Subject | Re: [PATCH 1/8] [I/OAT] DMA memcpy subsystem |
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On 3/16/06, Kumar Gala <galak@kernel.crashing.org> wrote: > It would seem that when a client registers (or shortly there after > when they call dma_async_client_chan_request()) they would expect to > get the number of channels they need by some given time period. > > For example, lets say a client registers but no dma device exists. > They will never get called to be aware of this condition. > > I would think most clients would either spin until they have all the > channels they need or fall back to a non-async mechanism.
Clients *are* expected to fall back to non-async if they are not given channels. The reason it was implemented with callbacks for added/removed was that the client may be initializing before the channels are enumerated. For example, the net subsystem will ask for channels and not get them for a while, until the ioatdma PCI device is found and its driver loads. In this scenario, we'd like the net subsystem to be given these channels, instead of them going unused.
> Also, what do you think about adding an operation type (MEMCPY, XOR, > CRYPTO_AES, etc). We can than validate if the operation type > expected is supported by the devices that exist.
No objections, but this speculative support doesn't need to be in our initial patchset.
> Shouldn't we also have a dma_async_client_chan_free()?
Well we could just define it to be chan_request(0) but it doesn't seem to be needed. Also, the allocation mechanism we have for channels is different from alloc/free's semantics, so it may be best to not muddy the water in this area.
Regards -- Andy - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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