Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752667AbbEATiq (ORCPT ); Fri, 1 May 2015 15:38:46 -0400 Received: from mail-wg0-f43.google.com ([74.125.82.43]:36689 "EHLO mail-wg0-f43.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752537AbbEATiZ (ORCPT ); Fri, 1 May 2015 15:38:25 -0400 MIME-Version: 1.0 In-Reply-To: <1430507711.23761.182.camel@misato.fc.hp.com> References: <20150428181203.35812.60474.stgit@dwillia2-desk3.amr.corp.intel.com> <20150428182439.35812.81191.stgit@dwillia2-desk3.amr.corp.intel.com> <1430502493.23761.145.camel@misato.fc.hp.com> <1430504355.23761.153.camel@misato.fc.hp.com> <1430507711.23761.182.camel@misato.fc.hp.com> Date: Fri, 1 May 2015 12:38:23 -0700 Message-ID: Subject: Re: [Linux-nvdimm] [PATCH v2 05/20] libnd, nd_acpi: dimm/memory-devices From: Dan Williams To: Toshi Kani Cc: "linux-nvdimm@lists.01.org" , Neil Brown , Greg KH , "Rafael J. Wysocki" , Robert Moore , "linux-kernel@vger.kernel.org" , Linux ACPI Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4103 Lines: 76 On Fri, May 1, 2015 at 12:15 PM, Toshi Kani wrote: > On Fri, 2015-05-01 at 11:43 -0700, Dan Williams wrote: >> On Fri, May 1, 2015 at 11:19 AM, Toshi Kani wrote: >> > On Fri, 2015-05-01 at 11:22 -0700, Dan Williams wrote: >> >> On Fri, May 1, 2015 at 10:48 AM, Toshi Kani 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. >> > >> > By looking at the callers of is_namespace_pmem() and is_namespace_blk(), >> > such as nd_namespace_label_update(), I am concerned that the namespace >> > types are also used for indicating the presence a label. Is it OK for >> > nd_namespace_label_update() to do nothing when there is no aliasing? > > Did you forget to answer this question? I am not asking to have a > label. I am asking if the namespace types can handle it correctly. > Restating the nd_namespace_label_update() example: > - namespace_io case: Skip, but a label may still exist. Correct? > - namespace_blk case: Proceed, but blk does not require a label. Ah, ok. This is handled by nd_namespace_attr_visible() only labelled namespaces have writable sysfs attributes. This would need to be extended for a label-less BLK namespace type. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/