On Tue, Jan 06, 2026 at 07:51:12PM +0000, Pavel Begunkov wrote:

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But I am wondering why not make it as one subsystem interface, such as nvme ioctl, then the whole implementation can be simplified a lot. It is reasonable because subsystem is exactly the side for consuming/importing the dma-buf.

It's not an nvme specific interface, and so a file op was much more convenient.

It is the much better abstraction. Also the nvme subsystems is not an actor, and registering things to the subsystems does not work. The nvme controller is the entity that does the dma mapping, and this interface works very well for that.