[RFC 5/9] block: Add support functions for persistent durable name

[Tony Asleson <tasleson@xxxxxxxxxx>]

Add functions to retrieve and build durable name string into supplied
buffer for functions that log using struct device and struct scsi_device.

Signed-off-by: Tony Asleson <tasleson@xxxxxxxxxx>
---
 drivers/base/core.c        | 24 ++++++++++++++++++++++++
 drivers/scsi/scsi_lib.c    | 20 ++++++++++++++++++++
 drivers/scsi/scsi_sysfs.c  |  1 +
 include/linux/device.h     |  2 ++
 include/scsi/scsi_device.h |  3 +++
 5 files changed, 50 insertions(+)

diff --git a/drivers/base/core.c b/drivers/base/core.c
index 7bd9cd366d41..93cc1c45e9d3 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -2009,6 +2009,30 @@ int dev_set_name(struct device *dev, const char *fmt, ...)
 }
 EXPORT_SYMBOL_GPL(dev_set_name);
 
+/**
+ * dev_durable_name - Write "DURABLE_NAME"=<durable name> in buffer
+ * @dev: device
+ * @buffer: character buffer to write results
+ * @len: length of buffer
+ * @return Number of bytes written to buffer
+ */
+int dev_durable_name(const struct device *dev, char *buffer, size_t len)
+{
+	int tmp, dlen;
+
+	if (dev->type && dev->type->durable_name) {
+		tmp = snprintf(buffer, len, "DURABLE_NAME=");
+		if (tmp < len) {
+			dlen = dev->type->durable_name(dev, buffer + tmp,
+							len - tmp);
+			if (dlen > 0 && ((dlen + tmp) < len))
+				return dlen + tmp;
+		}
+	}
+	return 0;
+}
+EXPORT_SYMBOL_GPL(dev_durable_name);
+
 /**
  * device_to_dev_kobj - select a /sys/dev/ directory for the device
  * @dev: device
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 91c007d26c1e..f22e59253d9d 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -3120,3 +3120,23 @@ int scsi_vpd_tpg_id(struct scsi_device *sdev, int *rel_id)
 	return group_id;
 }
 EXPORT_SYMBOL(scsi_vpd_tpg_id);
+
+int dev_to_scsi_durable_name(const struct device *dev, char *buf, size_t len)
+{
+	return scsi_durable_name(to_scsi_device(dev), buf, len);
+}
+EXPORT_SYMBOL(dev_to_scsi_durable_name);
+
+int scsi_durable_name(struct scsi_device *sdev, char *buf, size_t len)
+{
+	int vpd_len = 0;
+
+	vpd_len = scsi_vpd_lun_id(sdev, buf, len);
+	if (vpd_len > 0 && vpd_len < len)
+		vpd_len = strim_dupe(buf) + 1;
+	else
+		vpd_len = 0;
+
+	return vpd_len;
+}
+EXPORT_SYMBOL(scsi_durable_name);
diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c
index 6d7362e7367e..ee5b8197916f 100644
--- a/drivers/scsi/scsi_sysfs.c
+++ b/drivers/scsi/scsi_sysfs.c
@@ -1560,6 +1560,7 @@ static struct device_type scsi_dev_type = {
 	.name =		"scsi_device",
 	.release =	scsi_device_dev_release,
 	.groups =	scsi_sdev_attr_groups,
+	.durable_name = dev_to_scsi_durable_name,
 };
 
 void scsi_sysfs_device_initialize(struct scsi_device *sdev)
diff --git a/include/linux/device.h b/include/linux/device.h
index dd4ac8db5f57..566f6be6ee0d 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -1350,6 +1350,8 @@ static inline const char *dev_name(const struct device *dev)
 extern __printf(2, 3)
 int dev_set_name(struct device *dev, const char *name, ...);
 
+int dev_durable_name(const struct device *d, char *buffer, size_t len);
+
 #ifdef CONFIG_NUMA
 static inline int dev_to_node(struct device *dev)
 {
diff --git a/include/scsi/scsi_device.h b/include/scsi/scsi_device.h
index 202f4d6a4342..1cb35e10f54a 100644
--- a/include/scsi/scsi_device.h
+++ b/include/scsi/scsi_device.h
@@ -455,6 +455,9 @@ extern void sdev_disable_disk_events(struct scsi_device *sdev);
 extern void sdev_enable_disk_events(struct scsi_device *sdev);
 extern int scsi_vpd_lun_id(struct scsi_device *, char *, size_t);
 extern int scsi_vpd_tpg_id(struct scsi_device *, int *);
+extern int dev_to_scsi_durable_name(const struct device *dev, char *buf,
+					size_t len);
+extern int scsi_durable_name(struct scsi_device *sdev, char *buf, size_t len);
 
 #ifdef CONFIG_PM
 extern int scsi_autopm_get_device(struct scsi_device *);
-- 
2.21.0