Re: [PATCH v2] nvme: enable FDP support

[Keith Busch <kbusch@kernel.org>]

On Mon, Jun 10, 2024 at 01:55:41PM +0200, Christoph Hellwig wrote:
> On Mon, Jun 10, 2024 at 07:27:16AM -0400, Martin K. Petersen wrote:
> > > And TP 4146 author list shows 10 companies. Perhaps good enough for 
> > > diverse opinions on how to go about things before settling down.
> > 
> > I think FDP and SCSI streams are less than ideal. 10+ years and the
> > standards bodies still haven't been able to produce an approach that
> > makes sense in the context of a general purpose operating system.
> 
> The SCSI temperature hints are I think exactly what we want.  The fact
> that they had to be shoe horned in in a weird to claim to be streams
> is a little awkward, but sometimes that's need to get things done.

I feel a bit out of the loop here, I'm not sure what the concern is.

I agree the FDP setup is complicated, but none of that is taken on by
the driver. It just discovers the capabilities and maps an arbitrary
software "hint" to an arbitrary device "hint". It's up to the
application to use those optimally; the driver just performs the
requested mapping.

Is it because the names of those hints indicate data lifetime? These are
just arbitrary numbers used by applications to separate placement. If
they were called HINT_A, HINT_B, HINT_C, would that make this ok?