nvme: report capacity 0 for non supported ZNS SSDs

[Javier Gonzalez]

On 03.11.2020 16:26, hch at lst.de wrote:
>On Tue, Nov 03, 2020 at 03:10:19PM +0100, Javier Gonzalez wrote:
>> One question here is that we are preparing a RFC for a io_uring passthru
>> using the block device. Based on this discussion, it seems to me that
>> you see this more suitable through the char device.
>>
>> Does it make sense that we post this RFC using the block device? It
>> would be helpful to get early feedback before starting the char device.
>
>If you wan to send the RFC with the block device that is ok.  But I
>think the separate character device is pretty trivial, at least for
>NVM command set derived command sets like ZNS (for others we'll need
>to finish the Command Set Independent Identify Namespace TP first).

Ok. Good to hear that we can do this in steps - I was worried that we
would need to cover this use case too in the beginning, which would
delay this work significantly.

>
>> I see that this does not make much sense for the other non-supported
>> features in this patch (i.e., !po2 zone size and zoc). Since this is
>> very much like PI today, is it OK we add these the same way (capacity 0)
>> and then move to the char device when ready?
>
>I'd rath avoid adding more of that capacity 0 mess if we can.  Especially
>as the character device should be really easy to do.

Ok. We will move ahead with the char device and port current capacity 0
there in the series.

Thanks for the guidance Christoph!