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Date: Mon, 14 Oct 2024 13:45:28 +0200
From: Christoph Hellwig <hch@lst.de>
To: Damien Le Moal <dlemoal@kernel.org>
Cc: Christoph Hellwig <hch@lst.de>, linux-nvme@lists.infradead.org,
	Keith Busch <kbusch@kernel.org>, Sagi Grimberg <sagi@grimberg.me>,
	Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>,
	Krzysztof =?utf-8?Q?Wilczy=C5=84ski?= <kw@linux.com>,
	Kishon Vijay Abraham I <kishon@kernel.org>,
	Bjorn Helgaas <bhelgaas@google.com>,
	Lorenzo Pieralisi <lpieralisi@kernel.org>,
	linux-pci@vger.kernel.org,
	Rick Wertenbroek <rick.wertenbroek@gmail.com>,
	Niklas Cassel <cassel@kernel.org>
Subject: Re: [PATCH v2 2/5] nvmef: export nvmef_create_ctrl()
Message-ID: <20241014114528.GA31937@lst.de>
References: <20241011121951.90019-1-dlemoal@kernel.org> <20241011121951.90019-3-dlemoal@kernel.org> <20241014084219.GA23780@lst.de> <62ba5cda-338e-48bf-b82e-60e4721b1bfb@kernel.org>
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On Mon, Oct 14, 2024 at 06:10:36PM +0900, Damien Le Moal wrote:
> Nope, the PCIe "transport" is the front-end of the endpoint driver.
> What this patch does is to allow this driver to be created by passing it a
> string that is normally used for "nvme connect" command, which calls
> nvmf_create_ctrl().

That's a pretty wrong and broken layering.  PCIe isn't any different
than RDMA or TCP in being a NVMe transport.

> The entire thing was created to not add a PCIe host transport but rather to use
> a locally created fabric host controller which connect to whatever the user
> wants. That is: the PCI endpoint driver can implement a PCI interface which uses
> a loop nvme device, or a tcp nvme device (and if you have a board that can do
> rdma or fc, that can also be used as the backend nvme device used from the pci
> endpoint driver).

You can always use the nvmet passthrough backend to directly use a
nvme controller to export through nvmet.