Re: [PATCH] lightnvm: move device L2P detection to core

[Matias BjÃrling]

On 08/03/2018 02:40 PM, Javier Gonzalez wrote:
> > On 3 Aug 2018, at 14.37, Matias BjÃrling <mb@xxxxxxxxxxx> wrote:
> >
> > On 08/03/2018 02:16 PM, Javier Gonzalez wrote:
> > > > On 3 Aug 2018, at 10.54, Matias BjÃrling <mb@xxxxxxxxxxx> wrote:
> > > >
> > > > A 1.2 device is able to manage the logical to physical mapping
> > > > table internally or leave it to the host.
> > > >
> > > > A target only supports one of those approaches, and therefore must
> > > > check on initialization. Move this check to core to avoid each target
> > > > implement the check.
> > > >
> > > > Signed-off-by: Matias BjÃrling <mb@xxxxxxxxxxx>
> > > > ---
> > > I see where you want to go with these changes, but the way targets are
> > > layered on top of the LightNVM subsystem does not align with it.
> > > LightNVM can support different OCSSD versions and capabilities, but that
> > > does not mean that a target (e.g., pblk) does. The way I see it, core
> > > should only check for (i) the drive to expose itself in a known revision
> > > and (ii) the reported structures to be consistent. However, specific
> > > functionality is not for core to check upo.
> >
> > Why try to initialize a target, if we already know that it is incompatible?
>
> Yes, that is my point. But the one who knows if the targets supports
> something or not is the target, not the subsystem. Here, you are making
> an assumption knowing the pblk requires the L2P on the host, but that
> could change in the future...

I don't believe it can. It is not supported by the 2.0 specification. 
1.2 is legacy.

I understand this from the perspective when checking for un-even 
configurations using the geometry. But this is a spec incompatibility, 
which I don't think the target should care about.