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Subject: Re: [PATCH v2] nvme: allow 64-bit results in passthru commands
To:     Keith Busch <kbusch@kernel.org>,
        Marta Rybczynska <mrybczyn@kalray.eu>
Cc:     Christoph Hellwig <hch@lst.de>, axboe <axboe@fb.com>,
        linux-nvme <linux-nvme@lists.infradead.org>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        Samuel Jones <sjones@kalray.eu>,
        Guillaume Missonnier <gmissonnier@kalray.eu>
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From:   Sagi Grimberg <sagi@grimberg.me>
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Date:   Mon, 19 Aug 2019 11:56:28 -0700
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>> ----- On 16 Aug, 2019, at 15:16, Christoph Hellwig hch@lst.de wrote:
>>> Sorry for not replying to the earlier version, and thanks for doing
>>> this work.
>>>
>>> I wonder if instead of using our own structure we'd just use
>>> a full nvme SQE for the input and CQE for that output.  Even if we
>>> reserve a few fields that means we are ready for any newly used
>>> field (at least until the SQE/CQE sizes are expanded..).
>>
>> We could do that, nvme_command and nvme_completion are already UAPI.
>> On the other hand that would mean not filling out certain fields like
>> command_id. Can do an approach like this.
> 
> Well, we need to pass user space addresses and lengths, which isn't
> captured in struct nvme_command.

Isn't simply having a 64 variant simpler?