Merge branch 'libnvdimm-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm

Pull libnvdimm fix from Dan Williams:
 "This contains a regression fix for a problem that was introduced in
  v4.7-rc6.

  In 4.7-rc1 we introduced auto-probing for the ACPI DSM (device-
  specific-method) format that the platform firmware implements for
  nvdimm devices.  We initially fixed a regression in probing the QEMU
  DSM implementation by making acpi_check_dsm() tolerant of the way QEMU
  reports the "0 DSMs supported" condition.

  However, that broke HPE platforms since that tolerance caused the
  driver to mistakenly match the 1-zero-byte response those platforms
  give to "unknown" commands.  Instead, we simply make the driver
  tolerant of not finding any supported DSMs.  This has been tested to
  work with both QEMU and HPE platforms.

  This commit has appeared in a -next release with no reported issues"

* 'libnvdimm-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm:
  nfit: make DIMM DSMs optional

2 files changed, 9 insertions, 8 deletions

diff --git a/drivers/acpi/nfit.c b/drivers/acpi/nfit.c
index ac6ddcc080d4..1f0e06065ae6 100644
--- a/drivers/acpi/nfit.c
+++ b/drivers/acpi/nfit.c
@@ -1131,11 +1131,11 @@ static int acpi_nfit_add_dimm(struct acpi_nfit_desc *acpi_desc,
 
 	/*
 	 * Until standardization materializes we need to consider up to 3
-	 * different command sets.  Note, that checking for zero functions
-	 * tells us if any commands might be reachable through this uuid.
+	 * different command sets.  Note, that checking for function0 (bit0)
+	 * tells us if any commands are reachable through this uuid.
 	 */
 	for (i = NVDIMM_FAMILY_INTEL; i <= NVDIMM_FAMILY_HPE2; i++)
-		if (acpi_check_dsm(adev_dimm->handle, to_nfit_uuid(i), 1, 0))
+		if (acpi_check_dsm(adev_dimm->handle, to_nfit_uuid(i), 1, 1))
 			break;
 
 	/* limit the supported commands to those that are publicly documented */
@@ -1151,9 +1151,10 @@ static int acpi_nfit_add_dimm(struct acpi_nfit_desc *acpi_desc,
 		if (disable_vendor_specific)
 			dsm_mask &= ~(1 << 8);
 	} else {
-		dev_err(dev, "unknown dimm command family\n");
+		dev_dbg(dev, "unknown dimm command family\n");
 		nfit_mem->family = -1;
-		return force_enable_dimms ? 0 : -ENODEV;
+		/* DSMs are optional, continue loading the driver... */
+		return 0;
 	}
 
 	uuid = to_nfit_uuid(nfit_mem->family);
diff --git a/drivers/acpi/utils.c b/drivers/acpi/utils.c
index b4de130f2d57..22c09952e177 100644
--- a/drivers/acpi/utils.c
+++ b/drivers/acpi/utils.c
@@ -680,6 +680,9 @@ bool acpi_check_dsm(acpi_handle handle, const u8 *uuid, u64 rev, u64 funcs)
 	u64 mask = 0;
 	union acpi_object *obj;
 
+	if (funcs == 0)
+		return false;
+
 	obj = acpi_evaluate_dsm(handle, uuid, rev, 0, NULL);
 	if (!obj)
 		return false;
@@ -692,9 +695,6 @@ bool acpi_check_dsm(acpi_handle handle, const u8 *uuid, u64 rev, u64 funcs)
 			mask |= (((u64)obj->buffer.pointer[i]) << (i * 8));
 	ACPI_FREE(obj);
 
-	if (funcs == 0)
-		return true;
-
 	/*
 	 * Bit 0 indicates whether there's support for any functions other than
 	 * function 0 for the specified UUID and revision.