[RFC PATCH v2 1/7] struct device: Add function callback durable_name

[Tony Asleson <tasleson@redhat.com>]

Function callback and function to be used to write a persistent
durable name to the supplied character buffer.  This will be used to add
structured key-value data to log messages for hardware related errors
which allows end users to correlate message and specific hardware.

Signed-off-by: Tony Asleson <tasleson@redhat.com>
---
 drivers/base/core.c    | 24 ++++++++++++++++++++++++
 include/linux/device.h |  4 ++++
 2 files changed, 28 insertions(+)

diff --git a/drivers/base/core.c b/drivers/base/core.c
index dbb0f9130f42..86ea3acb1e1f 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -2281,6 +2281,30 @@ 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 && dev->durable_name) {
+		tmp = snprintf(buffer, len, "DURABLE_NAME=");
+		if (tmp < len) {
+			dlen = dev->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/include/linux/device.h b/include/linux/device.h
index fa04dfd22bbc..a9e5abbd2269 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -616,6 +616,8 @@ struct device {
 	struct iommu_fwspec	*iommu_fwspec;
 	struct iommu_param	*iommu_param;
 
+	int (*durable_name)(const struct device *dev, char *buff, size_t len);
+
 	bool			offline_disabled:1;
 	bool			offline:1;
 	bool			of_node_reused:1;
@@ -657,6 +659,8 @@ 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)
 {
-- 
2.25.4