tools/testing/nvdimm: allow custom error code injection

Given that libnvdimm driver stack takes specific actions on DIMM command
error codes like -EACCES, provide a facility to inject custom failures.
Signed-off-by: NDan Williams <dan.j.williams@intel.com>

tools/testing/nvdimm/test/nfit.c

@@ -138,6 +138,7 @@ static u32 handle[] = {
 };
 
 static unsigned long dimm_fail_cmd_flags[NUM_DCR];
+static int dimm_fail_cmd_code[NUM_DCR];
 
 struct nfit_test_fw {
 	enum intel_fw_update_state state;
@@ -892,8 +893,11 @@ static int get_dimm(struct nfit_mem *nfit_mem, unsigned int func)
 	if (i >= ARRAY_SIZE(handle))
 		return -ENXIO;
 
-	if ((1 << func) & dimm_fail_cmd_flags[i])
+	if ((1 << func) & dimm_fail_cmd_flags[i]) {
+		if (dimm_fail_cmd_code[i])
+			return dimm_fail_cmd_code[i];
 		return -EIO;
+	}
 
 	return i;
 }
@@ -1225,8 +1229,40 @@ static ssize_t fail_cmd_store(struct device *dev, struct device_attribute *attr,
 }
 static DEVICE_ATTR_RW(fail_cmd);
 
+static ssize_t fail_cmd_code_show(struct device *dev, struct device_attribute *attr,
+		char *buf)
+{
+	int dimm = dimm_name_to_id(dev);
+
+	if (dimm < 0)
+		return dimm;
+
+	return sprintf(buf, "%d\n", dimm_fail_cmd_code[dimm]);
+}
+
+static ssize_t fail_cmd_code_store(struct device *dev, struct device_attribute *attr,
+		const char *buf, size_t size)
+{
+	int dimm = dimm_name_to_id(dev);
+	unsigned long val;
+	ssize_t rc;
+
+	if (dimm < 0)
+		return dimm;
+
+	rc = kstrtol(buf, 0, &val);
+	if (rc)
+		return rc;
+
+	dimm_fail_cmd_code[dimm] = val;
+	return size;
+}
+static DEVICE_ATTR_RW(fail_cmd_code);
+
+
 static struct attribute *nfit_test_dimm_attributes[] = {
 	&dev_attr_fail_cmd.attr,
+	&dev_attr_fail_cmd_code.attr,
 	&dev_attr_handle.attr,
 	NULL,
 };