[PATCH] nvme: fix lightnvm check
hch at lst.de
Thu Sep 7 05:20:46 PDT 2017
On Thu, Sep 07, 2017 at 02:15:52PM +0200, Matias Bjørling wrote:
> I must have misunderstood when we discussed it. I understood it as to add
> detection to the NVMe specification.
> Going with Class code might not be the right way due to them describing the
> base protocol.
Well - existing NVMe (except Linux with lighnvm) simply expect a NVMe
PCIe device to support the NVM I/O command set. So if you have a drive
that wants to speak a different one it needs to be bindable to a new
driver and thus have a different PCIe class code.
But even with that in place we should also have the new command set
in CAP - so that a common code base can work all these devices, and
the command set can be used over fabrics as well for example.
> bit. Another approach, as OCSSD has grown, might be to use the existing
> command set, and teach the identify command about Zones/Chunks, where one
> writes sequentially within.
Even then we need a way to identify such devices. SCSI is a great
example - if the device has zones that MUST be written sequentially
it's a new ZBC device type. If the device just wants zones to be
written sequentially but can handle random writes with a performance
penalty it's the good old SBC type with a few extensions.
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