On Friday, May 01, 2015 09:23:38 AM Dan Williams wrote: > On Thu, Apr 30, 2015 at 6:21 PM, Rafael J. Wysocki <rjw@xxxxxxxxxxxxx> wrote: > > On Thursday, April 30, 2015 05:39:06 PM Dan Williams wrote: > >> On Thu, Apr 30, 2015 at 4:23 PM, Rafael J. Wysocki <rjw@xxxxxxxxxxxxx> wrote: > [..] > >> >> +if ND_DEVICES > >> >> + > >> >> +config LIBND > >> >> + tristate "LIBND: libnd device driver support" > >> >> + help > >> >> + Platform agnostic device model for a libnd bus. Publishes > >> >> + resources for a PMEM (persistent-memory) driver and/or BLK > >> >> + (sliding mmio window(s)) driver to attach. Exposes a device > >> >> + topology under a "ndX" bus device, a "/dev/ndctlX" bus-ioctl > >> >> + message passing interface, and a "/dev/nmemX" dimm-ioctl > >> >> + message interface for each memory device registered on the > >> >> + bus. instance. A userspace library "ndctl" provides an API > >> >> + to enumerate/manage this subsystem. > >> >> + > >> >> +config ND_ACPI > >> >> + tristate "ACPI: NFIT to libnd bus support" > >> >> + select LIBND > >> >> + depends on ACPI > >> >> + help > >> >> + Infrastructure to probe ACPI 6 compliant platforms for > >> >> + NVDIMMs (NFIT) and register a libnd device tree. In > >> >> + addition to storage devices this also enables libnd craft > >> >> + ACPI._DSM messages for platform/dimm configuration. > >> > > >> > I'm wondering if the two CONFIG options above really need to be user-selectable? > >> > > >> > For example, what reason people (who've already selected ND_DEVICES) may have > >> > for not selecting ND_ACPI if ACPI is set? > >> > >> > >> Later on in the series we introduce ND_E820 which supports creating a > >> libnd-bus from e820-type-12 memory ranges on pre-NFIT systems. I'm > >> also considering a configfs defined libnd-bus because e820 types are > >> not nearly enough information to safely define nvdimm resources > >> outside of NFIT. > > > > I hope these are not mutually exclusive with ND_ACPI? Otherwise distros > > will have problems with supporting them in one kernel. > > You can have ND_E820 support and ND_ACPI support in the same system. > Likely an NFIT enabled system will never have e820-type-12 ranges, but > if a user messes up and uses the new memmap=ss!nn command line to > overlap NFIT-defined memory then the request_mem_region() calls in the > driver will collide. First to load wins in that scenario. > > > If ND_E820 and ND_ACPI aren't mutually exclusive, I still don't see a good > > enough reason for asking users about ND_ACPI. Why would I ever say "No" > > here if I said "Yes" or "Module" to ND_DEVICES? > > I agree that if the user selects ND_DEVICES then ND_ACPI should > probably default on, but otherwise turning it off is a useful option. > If you know your system is pre-ACPI-6 then why bother including > support? If you're a distro, you don't care. You have to support it regardless. You might care if you're an end user building a kernel for yourself and just for this particular specific machine. Honestly, how many *server* users do that? And fewer user-selectable options means fewer combination of options to test during development/validation. Also unrelated, but applies to this patch. Since your new driver will handle device ID ACPI0012 which is defined by the spec proper, it should go into drivers/acpi/, because there's where such things go as a rule. -- I speak only for myself. Rafael J. Wysocki, Intel Open Source Technology Center. -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
