[RFC PATCH v2 6/7] scsi: Add durable_name for dev_printk

[Tony Asleson <tasleson@redhat.com>]

Add the needed functions to fill out the durable_name function
call back for scsi based storage devices.  This allows calls
into dev_printk for scsi devices to have a persistent id
associated with them.

Signed-off-by: Tony Asleson <tasleson@redhat.com>
---
 drivers/scsi/scsi_lib.c    | 14 ++++++++++++++
 drivers/scsi/scsi_sysfs.c  | 23 +++++++++++++++++++++++
 drivers/scsi/sd.c          |  2 ++
 include/scsi/scsi_device.h |  3 +++
 4 files changed, 42 insertions(+)

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 610ee41fa54c..482e41ec23c2 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -3121,3 +3121,17 @@ int scsi_vpd_tpg_id(struct scsi_device *sdev, int *rel_id)
 	return group_id;
 }
 EXPORT_SYMBOL(scsi_vpd_tpg_id);
+
+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++;
+	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 677b5c5403d2..f09f5c94ebbd 100644
--- a/drivers/scsi/scsi_sysfs.c
+++ b/drivers/scsi/scsi_sysfs.c
@@ -1582,6 +1582,28 @@ static struct device_type scsi_dev_type = {
 	.groups =	scsi_sdev_attr_groups,
 };
 
+
+int dev_to_scsi_durable_name(const struct device *dev, char *buf, size_t len)
+{
+	struct scsi_device *sd_dev = NULL;
+
+	// When we go through dev_printk in the scsi layer, dev is embedded
+	// in a struct scsi_device.  When we go through the block layer,
+	// dev is embedded in struct genhd, thus we need different paths to
+	// retrieve the struct scsi_device to call scsi_durable_name.
+	if (dev->type == &scsi_dev_type) {
+		sd_dev = to_scsi_device(dev);
+	} else if (dev->parent && dev->parent->type == &scsi_dev_type) {
+		sd_dev = to_scsi_device(dev->parent);
+	} else {
+		// We have a pointer to something else, bail
+		return 0;
+	}
+
+	return scsi_durable_name(sd_dev, buf, len);
+}
+EXPORT_SYMBOL(dev_to_scsi_durable_name);
+
 void scsi_sysfs_device_initialize(struct scsi_device *sdev)
 {
 	unsigned long flags;
@@ -1591,6 +1613,7 @@ void scsi_sysfs_device_initialize(struct scsi_device *sdev)
 	device_initialize(&sdev->sdev_gendev);
 	sdev->sdev_gendev.bus = &scsi_bus_type;
 	sdev->sdev_gendev.type = &scsi_dev_type;
+	sdev->sdev_gendev.durable_name = dev_to_scsi_durable_name;
 	dev_set_name(&sdev->sdev_gendev, "%d:%d:%d:%llu",
 		     sdev->host->host_no, sdev->channel, sdev->id, sdev->lun);
 
diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index 2710a0e5ae6d..774f1a8910a2 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -3359,6 +3359,8 @@ static int sd_probe(struct device *dev)
 	gd->private_data = &sdkp->driver;
 	gd->queue = sdkp->device->request_queue;
 
+	disk_to_dev(gd)->durable_name = dev_to_scsi_durable_name;
+
 	/* defaults, until the device tells us otherwise */
 	sdp->sector_size = 512;
 	sdkp->capacity = 0;
diff --git a/include/scsi/scsi_device.h b/include/scsi/scsi_device.h
index f8312a3e5b42..496774ff79fc 100644
--- a/include/scsi/scsi_device.h
+++ b/include/scsi/scsi_device.h
@@ -459,6 +459,9 @@ 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 *);
-- 
2.25.4