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Subject[PATCH] libnvdimm, nfit: export an 'ecc_unit_size' sysfs attribute
When the nfit driver initializes it runs an ARS (Address Range Scrub)
operation across every pmem range. Part of that process involves
determining the ARS capabilities of a given address range. One of the
capabilities that is reported is the 'Clear Uncorrectable Error Range
Length Unit Size' (see: ACPI 6.2 section Function Index 1 -
Query ARS Capabilities). This property is of interest to userspace
software as it indicates the boundary at which the NVDIMM may need to
perform read-modify-write cycles to maintain ECC blocks.

Cc: Vishal Verma <>
Signed-off-by: Dan Williams <>
drivers/acpi/nfit/core.c | 11 +++++++++++
1 file changed, 11 insertions(+)

diff --git a/drivers/acpi/nfit/core.c b/drivers/acpi/nfit/core.c
index 2c5608b92578..03105648f9b1 100644
--- a/drivers/acpi/nfit/core.c
+++ b/drivers/acpi/nfit/core.c
@@ -1674,8 +1674,19 @@ static ssize_t range_index_show(struct device *dev,
static DEVICE_ATTR_RO(range_index);

+static ssize_t ecc_unit_size_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+ struct nd_region *nd_region = to_nd_region(dev);
+ struct nfit_spa *nfit_spa = nd_region_provider_data(nd_region);
+ return sprintf(buf, "%d\n", nfit_spa->clear_err_unit);
+static DEVICE_ATTR_RO(ecc_unit_size);
static struct attribute *acpi_nfit_region_attributes[] = {
+ &dev_attr_ecc_unit_size.attr,

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