Re: [PATCH ndctl 5/7] cxl/region: determine region type based on root decoder capability

["Verma, Vishal L" <vishal.l.verma@intel.com>]

On Tue, 2023-02-07 at 21:55 -0800, Dan Williams wrote:
> Vishal Verma wrote:
> > 
<..> 
> > +static void set_type_from_decoder(struct cxl_ctx *ctx, struct parsed_params *p)
> > +{
> > +       int num_cap = 0;
> > +
> > +       /* if param.type was explicitly specified, nothing to do here */
> > +       if (param.type)
> > +               return;
> > +
> > +       /*
> > +        * if the root decoder only has one type of capability, default
> > +        * to that mode for the region.
> > +        */
> > +       if (cxl_decoder_is_pmem_capable(p->root_decoder))
> > +               num_cap++;
> > +       if (cxl_decoder_is_volatile_capable(p->root_decoder))
> > +               num_cap++;
> > +
> > +       if (num_cap == 1) {
> > +               if (cxl_decoder_is_volatile_capable(p->root_decoder))
> > +                       p->mode = CXL_DECODER_MODE_RAM;
> > +               else if (cxl_decoder_is_pmem_capable(p->root_decoder))
> > +                       p->mode = CXL_DECODER_MODE_PMEM;
> > +       }
> 
> Is @num_cap needed? I.e. if this just does:
> 
>     if (cxl_decoder_is_volatile_capable(p->root_decoder))
>         p->mode = CXL_DECODER_MODE_RAM;
>     if (cxl_decoder_is_pmem_capable(p->root_decoder))
>         p->mode = CXL_DECODER_MODE_PMEM;
> 
> ...then it matches the changelog of defaulting to pmem if both types are
> set, and otherwise the single capability dominates.

Oh true, that's clever! I hope it isn't too clever for future-me when
coming across this and wondering what is happening, but for now I like
it, so I'll run with it :)