SCSI: Add basic infrastructure for transport host statistics

From: 	James.Smart@Emulex.Com

This patch adds the basic hooks to the scsi subsystem to 
support transport-specific statistics to be added to a host. 
Its basic nature follows the way in which net devices showed 
their statistics.
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>

drivers/scsi/hosts.c

@@ -82,8 +82,12 @@ void scsi_remove_host(struct Scsi_Host *shost)
 	if (shost->transportt->host_destroy)
 		shost->transportt->host_destroy(shost);
 	class_device_unregister(&shost->shost_classdev);
-	if (shost->transport_classdev.class)
-		class_device_unregister(&shost->transport_classdev);
+	if (shost->transport_classdev.class) {
+		if (shost->transportt->host_statistics)
+			sysfs_remove_group(&shost->transport_classdev.kobj,
+				shost->transportt->host_statistics);
+ 		class_device_unregister(&shost->transport_classdev);
+	}
 	device_del(&shost->shost_gendev);
 }
 EXPORT_SYMBOL(scsi_remove_host);

drivers/scsi/scsi_sysfs.c

@@ -716,6 +716,14 @@ int scsi_sysfs_add_host(struct Scsi_Host *shost)
  			if (error)
 				return error;
  		}
+
+		if (shost->transportt->host_statistics) {
+			error = sysfs_create_group(
+					&shost->transport_classdev.kobj,
+					shost->transportt->host_statistics);
+			if (error)
+				return error;
+		}
  	}
 
 	return 0;

include/scsi/scsi_transport.h

@@ -33,6 +33,7 @@ struct scsi_transport_template {
 	struct class *device_class;
 	struct class *target_class;
 	struct class *host_class;
+	struct attribute_group *host_statistics;
 
 	/* Constructor functions */
 	int (*device_setup)(struct scsi_device *);