"Alastair D'Silva" [off-list ref] writes:

how about drivers/nvdimm/ocxl/scm.c ? Or may be place the driver as an
ocxl driver.

There is another patch series that is moving this from device driver to
nvdimm core. 

https://lore.kernel.org/linux-mm/157309899529.1582359.15358067933360719580.stgit@dwillia2-desk3.amr.corp.intel.com (local)

+/**
+ * scm_ndctl_config_write() - Handle a ND_CMD_SET_CONFIG_DATA command from ndctl
+ * @scm_data: the SCM metadata
+ * @command: the incoming data to write
+ * Return: 0 on success, negative on failure
+ */
+static int scm_ndctl_config_write(struct scm_data *scm_data,
+				  struct nd_cmd_set_config_hdr *command)
+{
+	if (command->in_offset + command->in_length > SCM_LABEL_AREA_SIZE)
+		return -EINVAL;
+
+	memcpy_flushcache(scm_data->metadata_addr + command->in_offset, command->in_buf,
+			  command->in_length);
+
+	return 0;
+}
+
+/**
+ * scm_ndctl_config_read() - Handle a ND_CMD_GET_CONFIG_DATA command from ndctl
+ * @scm_data: the SCM metadata
+ * @command: the read request
+ * Return: 0 on success, negative on failure
+ */
+static int scm_ndctl_config_read(struct scm_data *scm_data,
+				 struct nd_cmd_get_config_data_hdr *command)
+{
+	if (command->in_offset + command->in_length > SCM_LABEL_AREA_SIZE)
+		return -EINVAL;
+
+	memcpy(command->out_buf, scm_data->metadata_addr + command->in_offset,
+	       command->in_length);
+

memcpy_mcsafe()?

+	return 0;
+}
+
+/**
+ * scm_ndctl_config_size() - Handle a ND_CMD_GET_CONFIG_SIZE command from ndctl
+ * @scm_data: the SCM metadata
+ * @command: the read request
+ * Return: 0 on success, negative on failure
+ */
+static int scm_ndctl_config_size(struct nd_cmd_get_config_size *command)
+{
+	command->status = 0;
+	command->config_size = SCM_LABEL_AREA_SIZE;
+	command->max_xfer = PAGE_SIZE;
+
+	return 0;
+}
+
+static int read_smart_attrib(struct scm_data *scm_data, u16 offset,
+			     struct scm_smart_attribs *attribs)
+{
+	u64 val;
+	int rc;
+	struct scm_smart_attrib *attrib;
+	u8 attrib_id;
+
+	rc = ocxl_global_mmio_read64(scm_data->ocxl_afu, offset, OCXL_LITTLE_ENDIAN,
+				     &val);
+	if (rc)
+		return rc;
+
+	attrib_id = (val >> 56) & 0xff;
+	switch (attrib_id) {
+	case SCM_SMART_ATTR_POWER_ON_HOURS:
+		attrib = &attribs->power_on_hours;
+		break;
+
+	case SCM_SMART_ATTR_TEMPERATURE:
+		attrib = &attribs->temperature;
+		break;
+
+	case SCM_SMART_ATTR_LIFE_REMAINING:
+		attrib = &attribs->life_remaining;
+		break;
+
+	default:
+		dev_err(&scm_data->dev, "Unknown smart attrib '%d'", attrib_id);
+		return -EFAULT;
+	}
+
+	attrib->id = attrib_id;
+	attrib->attribute_flags = (val >> 40) & 0xffff;
+	attrib->current_val = (val >> 32) & 0xff;
+	attrib->threshold_val = (val >> 24) & 0xff;
+	attrib->worst_val = (val >> 16) & 0xff;
+
+	rc = ocxl_global_mmio_read64(scm_data->ocxl_afu, offset + 0x08,
+				     OCXL_LITTLE_ENDIAN, &val);
+	if (rc)
+		return rc;
+
+	attrib->raw_val = val;
+
+	return 0;
+}
+
+static int scm_smart_offset_0x00(struct scm_data *scm_data, u32 *length)
+'

What is special about _0x00? 

{

+	int rc;
+	u64 val;
+
+	u16 data_identifier;
+	u32 data_length;
+
+	rc = ocxl_global_mmio_read64(scm_data->ocxl_afu,
+				     scm_data->admin_command.data_offset,
+				     OCXL_LITTLE_ENDIAN, &val);
+	if (rc)
+		return rc;
+
+	data_identifier = val >> 48;
+	data_length = val & 0xFFFFFFFF;
+
+	if (data_identifier != 0x534D) {
+		dev_err(&scm_data->dev,
+			"Bad data identifier for smart data, expected 'SM', got '%-.*s'\n",
+			2, (char *)&data_identifier);
+		return -EFAULT;
+	}
+
+	*length = data_length;
+	return 0;
+}
+
+static int scm_smart_update(struct scm_data *scm_data)
+{
+	u32 length, i;
+	int rc;
+
+	mutex_lock(&scm_data->admin_command.lock);
+
+	rc = scm_admin_command_request(scm_data, ADMIN_COMMAND_SMART);
+	if (rc)
+		goto out;
+
+	rc = scm_admin_command_execute(scm_data);
+	if (rc)
+		goto out;
+
+	rc = scm_admin_command_complete_timeout(scm_data, ADMIN_COMMAND_SMART);
+	if (rc < 0) {
+		dev_err(&scm_data->dev, "SMART timeout\n");
+		goto out;
+	}
+
+	rc = scm_admin_response(scm_data);
+	if (rc < 0)
+		goto out;
+	if (rc != STATUS_SUCCESS) {
+		scm_warn_status(scm_data, "Unexpected status from SMART", rc);
+		goto out;
+	}
+
+	rc = scm_smart_offset_0x00(scm_data, &length);
+	if (rc)
+		goto out;
+
+	length /= 0x10; // Length now contains the number of attributes
+
+	for (i = 0; i < length; i++)
+		read_smart_attrib(scm_data,
+				  scm_data->admin_command.data_offset + 0x08 + i * 0x10,
+				  &scm_data->smart);
+
+	rc = scm_admin_response_handled(scm_data);
+	if (rc)
+		goto out;
+
+	rc = 0;
+	goto out;
+
+out:
+	mutex_unlock(&scm_data->admin_command.lock);
+	return rc;
+}
+
+static int scm_ndctl_smart(struct scm_data *scm_data, void *buf,
+			   unsigned int buf_len)
+{
+	int rc;
+
+	if (buf_len != sizeof(scm_data->smart))
+		return -EINVAL;
+
+	rc = scm_smart_update(scm_data);
+	if (rc)
+		return rc;
+
+	memcpy(buf, &scm_data->smart, buf_len);
+
+	return 0;
+}
+
+
+static int scm_ndctl(struct nvdimm_bus_descriptor *nd_desc,
+		     struct nvdimm *nvdimm,
+		     unsigned int cmd, void *buf, unsigned int buf_len, int *cmd_rc)
+{
+	struct scm_data *scm_data = container_of(nd_desc, struct scm_data, bus_desc);
+
+	switch (cmd) {
+	case ND_CMD_SMART:
+		*cmd_rc = scm_ndctl_smart(scm_data, buf, buf_len);
+		return 0;
+
+	case ND_CMD_GET_CONFIG_SIZE:
+		*cmd_rc = scm_ndctl_config_size(buf);
+		return 0;
+
+	case ND_CMD_GET_CONFIG_DATA:
+		*cmd_rc = scm_ndctl_config_read(scm_data, buf);
+		return 0;
+
+	case ND_CMD_SET_CONFIG_DATA:
+		*cmd_rc = scm_ndctl_config_write(scm_data, buf);
+		return 0;
+
+	default:
+		return -ENOTTY;
+	}
+}
+
+static ssize_t serial_show(struct device *dev,
+			   struct device_attribute *attr, char *buf)
+{
+	struct nvdimm *nvdimm = to_nvdimm(dev);
+	struct scm_data *scm_data = nvdimm_provider_data(nvdimm);
+	const struct ocxl_fn_config *config = ocxl_function_config(scm_data->ocxl_fn);
+
+	return sprintf(buf, "0x%llx\n", config->serial);
+}
+static DEVICE_ATTR_RO(serial);
+
+static struct attribute *scm_dimm_attributes[] = {
+	&dev_attr_serial.attr,
+	NULL,
+};
+
+static umode_t scm_dimm_attr_visible(struct kobject *kobj,
+				     struct attribute *a, int n)
+{
+	return a->mode;
+}
+
+static const struct attribute_group scm_dimm_attribute_group = {
+	.name = "scm",
+	.attrs = scm_dimm_attributes,
+	.is_visible = scm_dimm_attr_visible,
+};
+

That is a generic name for dimm attribute

+static const struct attribute_group *scm_dimm_attribute_groups[] = {
+	&nvdimm_attribute_group,
+	&nd_device_attribute_group,
+	&scm_dimm_attribute_group,
+	NULL,
+};
+
+/**
+ * scm_reserve_metadata() - Reserve space for nvdimm metadata
+ * @scm_data: The SCM device data
+ * @lpc_mem: The resource representing the LPC memory of the SCM device
+ */
+static int scm_reserve_metadata(struct scm_data *scm_data,
+				struct resource *lpc_mem)
+{
+	scm_data->metadata_addr = devm_memremap(&scm_data->dev, lpc_mem->start,
+						SCM_LABEL_AREA_SIZE, MEMREMAP_WB);
+	if (IS_ERR(scm_data->metadata_addr))
+		return PTR_ERR(scm_data->metadata_addr);
+
+	return 0;
+}
+
+/**
+ * scm_overwrite() - Overwrite all data on the card
+ * @scm_data: The SCM device data
+ * Return: 0 on success
+ */
+int scm_overwrite(struct scm_data *scm_data)
+{
+	int rc;
+
+	mutex_lock(&scm_data->ns_command.lock);
+
+	rc = scm_ns_command_request(scm_data, NS_COMMAND_SECURE_ERASE);
+	if (rc)
+		goto out;
+
+	rc = scm_ns_command_execute(scm_data);
+	if (rc)
+		goto out;
+
+	scm_data->overwrite_state = SCM_OVERWRITE_BUSY;
+
+	return 0;
+
+out:
+	mutex_unlock(&scm_data->ns_command.lock);
+	return rc;
+}
+
+/**
+ * scm_secop_overwrite() - Overwrite all data on the card
+ * @nvdimm: The nvdimm representation of the SCM device to start the overwrite on
+ * @key_data: Unused (no security key implementation)
+ * Return: 0 on success
+ */
+static int scm_secop_overwrite(struct nvdimm *nvdimm,
+			       const struct nvdimm_key_data *key_data)
+{
+	struct scm_data *scm_data = nvdimm_provider_data(nvdimm);
+
+	return scm_overwrite(scm_data);
+}
+
+/**
+ * scm_secop_query_overwrite() - Get the current overwrite state
+ * @nvdimm: The nvdimm representation of the SCM device to start the overwrite on
+ * Return: 0 if successful or idle, -EBUSY if busy, -EFAULT if failed
+ */
+static int scm_secop_query_overwrite(struct nvdimm *nvdimm)
+{
+	struct scm_data *scm_data = nvdimm_provider_data(nvdimm);
+
+	if (scm_data->overwrite_state == SCM_OVERWRITE_BUSY)
+		return -EBUSY;
+
+	if (scm_data->overwrite_state == SCM_OVERWRITE_FAILED)
+		return -EFAULT;
+
+	return 0;
+}
+
+/**
+ * scm_secop_get_flags() - return the security flags for the SCM device
+ */
+static unsigned long scm_secop_get_flags(struct nvdimm *nvdimm,
+		enum nvdimm_passphrase_type ptype)
+{
+	struct scm_data *scm_data = nvdimm_provider_data(nvdimm);
+
+	if (scm_data->overwrite_state == SCM_OVERWRITE_BUSY)
+		return BIT(NVDIMM_SECURITY_OVERWRITE);
+
+	return BIT(NVDIMM_SECURITY_DISABLED);
+}
+
+static const struct nvdimm_security_ops sec_ops  = {
+	.get_flags = scm_secop_get_flags,
+	.overwrite = scm_secop_overwrite,
+	.query_overwrite = scm_secop_query_overwrite,
+};
+
+/**
+ * scm_register_lpc_mem() - Discover persistent memory on a device and register it with the NVDIMM subsystem
+ * @scm_data: The SCM device data
+ * Return: 0 on success
+ */
+static int scm_register_lpc_mem(struct scm_data *scm_data)
+{
+	struct nd_region_desc region_desc;
+	struct nd_mapping_desc nd_mapping_desc;
+	struct resource *lpc_mem;
+	const struct ocxl_afu_config *config;
+	const struct ocxl_fn_config *fn_config;
+	int rc;
+	unsigned long nvdimm_cmd_mask = 0;
+	unsigned long nvdimm_flags = 0;
+	int target_node;
+	char serial[16+1];
+
+	// Set up the reserved metadata area
+	rc = ocxl_afu_map_lpc_mem(scm_data->ocxl_afu);
+	if (rc < 0)
+		return rc;
+
+	lpc_mem = ocxl_afu_lpc_mem(scm_data->ocxl_afu);
+	if (lpc_mem == NULL)
+		return -EINVAL;
+
+	config = ocxl_afu_config(scm_data->ocxl_afu);
+	fn_config = ocxl_function_config(scm_data->ocxl_fn);
+
+	rc = scm_reserve_metadata(scm_data, lpc_mem);
+	if (rc)
+		return rc;
+
+	scm_data->bus_desc.attr_groups = scm_pmem_attribute_groups;
+	scm_data->bus_desc.provider_name = "scm";
+	scm_data->bus_desc.ndctl = scm_ndctl;
+	scm_data->bus_desc.module = THIS_MODULE;
+
+	scm_data->nvdimm_bus = nvdimm_bus_register(&scm_data->dev,
+			       &scm_data->bus_desc);
+	if (!scm_data->nvdimm_bus)
+		return -EINVAL;
+
+	scm_data->scm_res.start = (u64)lpc_mem->start + SCM_LABEL_AREA_SIZE;
+	scm_data->scm_res.end = (u64)lpc_mem->start + config->lpc_mem_size - 1;
+	scm_data->scm_res.name = "SCM persistent memory";
+
+	set_bit(ND_CMD_GET_CONFIG_SIZE, &nvdimm_cmd_mask);
+	set_bit(ND_CMD_GET_CONFIG_DATA, &nvdimm_cmd_mask);
+	set_bit(ND_CMD_SET_CONFIG_DATA, &nvdimm_cmd_mask);
+	set_bit(ND_CMD_SMART, &nvdimm_cmd_mask);
+
+	set_bit(NDD_ALIASING, &nvdimm_flags);
+
+	snprintf(serial, sizeof(serial), "%llx", fn_config->serial);
+	nd_mapping_desc.nvdimm = __nvdimm_create(scm_data->nvdimm_bus, scm_data,
+				 scm_dimm_attribute_groups,
+				 nvdimm_flags, nvdimm_cmd_mask,
+				 0, NULL, serial, &sec_ops);

nvdimm_create()?

+	if (!nd_mapping_desc.nvdimm)
+		return -ENOMEM;
+
+	if (nvdimm_bus_check_dimm_count(scm_data->nvdimm_bus, 1))
+		return -EINVAL;
+
+	nd_mapping_desc.start = scm_data->scm_res.start;
+	nd_mapping_desc.size = resource_size(&scm_data->scm_res);
+	nd_mapping_desc.position = 0;
+
+	scm_data->nd_set.cookie1 = fn_config->serial + 1; // allow for empty serial
+	scm_data->nd_set.cookie2 = fn_config->serial + 1;
+
+	target_node = of_node_to_nid(scm_data->pdev->dev.of_node);
+
+	memset(&region_desc, 0, sizeof(region_desc));
+	region_desc.res = &scm_data->scm_res;
+	region_desc.attr_groups = scm_pmem_region_attribute_groups;
+	region_desc.numa_node = NUMA_NO_NODE;
+	region_desc.target_node = target_node;
+	region_desc.num_mappings = 1;
+	region_desc.mapping = &nd_mapping_desc;
+	region_desc.nd_set = &scm_data->nd_set;
+
+	set_bit(ND_REGION_PAGEMAP, &region_desc.flags);
+	/*
+	 * NB: libnvdimm copies the data from ndr_desc into it's own
+	 * structures so passing a stack pointer is fine.
+	 */
+	scm_data->nd_region = nvdimm_pmem_region_create(scm_data->nvdimm_bus,
+			      &region_desc);
+	if (!scm_data->nd_region)
+		return -EINVAL;
+
+	dev_info(&scm_data->dev,
+		 "Onlining %lluMB of persistent memory\n",
+		 nd_mapping_desc.size / SZ_1M);
+
+	return 0;
+}
+

Would it be possible to split the driver such that we add features like
security ops in later patch? Can this patch be a baisc dirver that just get
the nvdimm initialized. Any attribute specific to ocxl can be exported
in follow up patches?

-aneesh