[SCSI] scsi_transport_sas: add expander backlink

This patch adds the ability to add a backlink to a particular port.  The
idea is to represent properly ports on expanders that are used
specifically for linking to the parent device in the topology.

Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>

2 files changed, 23 insertions, 0 deletions

diff --git a/drivers/scsi/scsi_transport_sas.c b/drivers/scsi/scsi_transport_sas.c
index 9bb4e37a1a61..7871bc25fafb 100644
--- a/drivers/scsi/scsi_transport_sas.c
+++ b/drivers/scsi/scsi_transport_sas.c
@@ -692,6 +692,13 @@ void sas_port_delete(struct sas_port *port)
         }
         mutex_unlock(&port->phy_list_mutex);
 
+        if (port->is_backlink) {
+                struct device *parent = port->dev.parent;
+
+                sysfs_remove_link(&port->dev.kobj, parent->bus_id);
+                port->is_backlink = 0;
+        }
+
         transport_remove_device(dev);
         device_del(dev);
         transport_destroy_device(dev);
@@ -767,6 +774,19 @@ void sas_port_delete_phy(struct sas_port *port, struct sas_phy *phy)
 }
 EXPORT_SYMBOL(sas_port_delete_phy);
 
+void sas_port_mark_backlink(struct sas_port *port)
+{
+        struct device *parent = port->dev.parent->parent->parent;
+
+        if (port->is_backlink)
+                return;
+        port->is_backlink = 1;
+        sysfs_create_link(&port->dev.kobj, &parent->kobj,
+                          parent->bus_id);
+
+}
+EXPORT_SYMBOL(sas_port_mark_backlink);
+
 /*
  * SAS remote PHY attributes.
  */
diff --git a/include/scsi/scsi_transport_sas.h b/include/scsi/scsi_transport_sas.h
index f5772ff61d0d..6cc2314098cf 100644
--- a/include/scsi/scsi_transport_sas.h
+++ b/include/scsi/scsi_transport_sas.h
@@ -130,6 +130,8 @@ struct sas_port {
 
         int                     port_identifier;
         int                     num_phys;
+        /* port flags */
+        unsigned int            is_backlink:1;
 
         /* the other end of the link */
         struct sas_rphy         *rphy;
@@ -175,6 +177,7 @@ void sas_port_free(struct sas_port *);
 void sas_port_delete(struct sas_port *);
 void sas_port_add_phy(struct sas_port *, struct sas_phy *);
 void sas_port_delete_phy(struct sas_port *, struct sas_phy *);
+void sas_port_mark_backlink(struct sas_port *);
 int scsi_is_sas_port(const struct device *);
 
 extern struct scsi_transport_template *