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Date:   Mon, 19 Aug 2019 12:57:49 -0600
From:   Keith Busch <kbusch@kernel.org>
To:     Sagi Grimberg <sagi@grimberg.me>
Cc:     Marta Rybczynska <mrybczyn@kalray.eu>,
        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>
Subject: Re: [PATCH v2] nvme: allow 64-bit results in passthru commands
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On Mon, Aug 19, 2019 at 11:56:28AM -0700, Sagi Grimberg wrote:
> 
> >> ----- 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?

Could you provide more details on what you mean by this?