Re: [Linux-nvdimm] [PATCH v2 05/20] libnd, nd_acpi: dimm/memory-devices

Toshi Kani
2015-05-01T18:07:15Z

On Tue, 2015-04-28 at 14:24 -0400, Dan Williams wrote:
> Register the memory devices described in the nfit as libnd 'dimm'
> devices on an nd bus. The kernel assigned device id for dimms is
> dynamic. If userspace needs a more static identifier it should consult
> a provider-specific attribute. In the case where NFIT is the provider,
> the 'nmemX/nfit/handle' or 'nmemX/nfit/serial' attributes may be used
> for this purpose.
:
> +
> +static int nd_acpi_register_dimms(struct acpi_nfit_desc *acpi_desc)
> +{
> + struct nfit_mem *nfit_mem;
> +
> + list_for_each_entry(nfit_mem, &acpi_desc->dimms, list) {
> + struct nd_dimm *nd_dimm;
> + unsigned long flags = 0;
> + u32 nfit_handle;
> +
> + nfit_handle = __to_nfit_memdev(nfit_mem)->nfit_handle;
> + nd_dimm = nd_acpi_dimm_by_handle(acpi_desc, nfit_handle);
> + if (nd_dimm) {
> + /*
> + * If for some reason we find multiple DCRs the
> + * first one wins
> + */
> + dev_err(acpi_desc->dev, "duplicate DCR detected: %s\n",
> + nd_dimm_name(nd_dimm));
> + continue;
> + }
> +
> + if (nfit_mem->bdw && nfit_mem->memdev_pmem)
> + flags |= NDD_ALIASING;

Does this check work for a NVDIMM card which has multiple pmem regions
with label info, but does not have any bdw region configured?

The code assumes that namespace_pmem (NDD_ALIASING) and namespace_blk
have label info. There may be an NVDIMM card with a single blk region
without label info.

Instead of using the namespace types to assume the label info, how about
adding a flag to indicate the presence of the label info? This avoids
the separation of namespace_io and namespace_pmem for the same pmem
driver.

Thanks,
-Toshi