11:22 a.m.
On Fri, May 1, 2015 at 10:48 AM, Toshi Kani <toshi.kani(a)hp.com> wrote:
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?
If you have multiple pmem regions then you don't have aliasing and
don't need a label. You'll get an nd_namespace_io per region.
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.
I'd really like to suggest that labels are only for resolving aliasing
and that if you have a BLK-only NVDIMM you'll get an automatic
namespace created the same as a PMEM-only. Partitioning is always
there to provide sub-divisions of a namespace. The only reason to
support multiple BLK-namespaces per-region is to give each a different
sector size. I may eventually need to relent on this position, but
I'd really like to understand the use case for requiring labels when
aliasing is not present as it seems like a waste to me.
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.
To what benefit?