Re: [PATCH v6 1/3] ublk: add opcode offsets for DRV_IN/DRV_OUT

[Andreas Hindborg (Samsung)]

Christoph Hellwig <hch@xxxxxxxxxxxxx> writes:

> On Tue, Jul 11, 2023 at 11:02:15AM +0200, Andreas Hindborg (Samsung) wrote:
>> 
>> Christoph Hellwig <hch@xxxxxxxxxxxxx> writes:
>> 
>> > On Tue, Jul 11, 2023 at 08:23:40AM +0200, Andreas Hindborg (Samsung) wrote:
>> >> Yet most on-the-wire protocols for actual hardware does support this
>> >> some way or another.
>> >
>> > Supports what?  Passthrough?  No.
>> 
>> Both SCSI and NVMe has command identifier ranges reserved for vendor
>> specific commands. I would assume that one use of these is to implement
>> passthrough channels to a device for testing out new interfaces. Just
>> guessing though.
>
> Vendor specific commands is an entirely different concept from Linux
> passthrough requests.

And yet they are somewhat similar, in the sense that they allow the user
of a protocol to express semantics that is not captured in the
established protocol. Uring command passthrough -> request passthrough
-> vendor specific commands. They sort of map well in terms of what they
allow the user to achieve. Or did I misunderstand something completely?