linux-kernel - Re: [Linux-nvdimm] [PATCH 04/21] nd: create an 'nd_bus' from an 'nfit

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Date:	Tue, 21 Apr 2015 13:55:56 -0600
From:	Toshi Kani <toshi.kani@...com>
To:	Dan Williams <dan.j.williams@...el.com>
Cc:	"linux-nvdimm@...ts.01.org" <linux-nvdimm@...ts.01.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [Linux-nvdimm] [PATCH 04/21] nd: create an 'nd_bus' from an
 'nfit_desc'

On Tue, 2015-04-21 at 12:58 -0700, Dan Williams wrote:
> On Tue, Apr 21, 2015 at 12:35 PM, Toshi Kani <toshi.kani@...com> wrote:
> > On Fri, 2015-04-17 at 21:35 -0400, Dan Williams wrote:
> >  :
> >> +
> >> +static int nd_mem_init(struct nd_bus *nd_bus)
> >> +{
> >> +     struct nd_spa *nd_spa;
> >> +
> >> +     /*
> >> +      * For each SPA-DCR address range find its corresponding
> >> +      * MEMDEV(s).  From each MEMDEV find the corresponding DCR.
> >> +      * Then, try to find a SPA-BDW and a corresponding BDW that
> >> +      * references the DCR.  Throw it all into an nd_mem object.
> >> +      * Note, that BDWs are optional.
> >> +      */
> >> +     list_for_each_entry(nd_spa, &nd_bus->spas, list) {
> >> +             u16 spa_index = readw(&nd_spa->nfit_spa->spa_index);
> >> +             int type = nfit_spa_type(nd_spa->nfit_spa);
> >> +             struct nd_mem *nd_mem, *found;
> >> +             struct nd_memdev *nd_memdev;
> >> +             u16 dcr_index;
> >> +
> >> +             if (type != NFIT_SPA_DCR)
> >> +                     continue;
> >
> > This function requires NFIT_SPA_DCR, SPA Range Structure with NVDIMM
> > Control Region GUID, for initializing an nd_mem object.  However,
> > battery-backed DIMMs do not have such control region SPA.  IIUC, the
> > NFIT spec does not require NFIT_SPA_DCR.
> >
> > Can you change this function to work with NFIT_SPA_PM as well?
> 
> NFIT_SPA_PM ranges are handled separately from nd_mem_init().  See
> nd_region_create() in patch 10.

If nd_mem_init() does not initialize nd_mem objects, nd_bus_probe() in
core.c fails in nd_bus_init_interleave_sets() and skips all subsequent
nd_bus_xxx() calls.  So, nd_region_create() won't be called.

nd_bus_init_interleave_sets() fails because init_interleave_set()
returns -ENODEV if (!nd_mem).

BTW, there are two nd_bus_probe() in bus.c and core.c, which is
confusing.

Thanks,
-Toshi


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