mtd: blktrans: allow FTL drivers to export sysfs attributes

This patch adds an ability to export sysfs attributes below
the block disk device.

This can be used to pass the udev an information about the FTL
and could include the vendor, serial, version, etc...
Signed-off-by: Maxim Levitsky <maximlevitsky@gmail.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

drivers/mtd/mtd_blkdevs.c

@@ -379,6 +379,10 @@ int add_mtd_blktrans_dev(struct mtd_blktrans_dev *new)
 		set_disk_ro(gd, 1);
 
 	add_disk(gd);
+
+	if (new->disk_attributes)
+		sysfs_create_group(&disk_to_dev(gd)->kobj,
+					new->disk_attributes);
 	return 0;
 error4:
 	module_put(tr->owner);
@@ -405,6 +409,10 @@ int del_mtd_blktrans_dev(struct mtd_blktrans_dev *old)
 	/* Stop new requests to arrive */
 	del_gendisk(old->disk);
 
+	if (old->disk_attributes)
+		sysfs_remove_group(&disk_to_dev(old->disk)->kobj,
+						old->disk_attributes);
+
 	/* Stop the thread */
 	kthread_stop(old->thread);
 

include/linux/mtd/blktrans.h

@@ -10,6 +10,7 @@
 
 #include <linux/mutex.h>
 #include <linux/kref.h>
+#include <linux/sysfs.h>
 
 struct hd_geometry;
 struct mtd_info;
@@ -28,6 +29,7 @@ struct mtd_blktrans_dev {
 	int open;
 	struct kref ref;
 	struct gendisk *disk;
+	struct attribute_group *disk_attributes;
 	struct task_struct *thread;
 	struct request_queue *rq;
 	spinlock_t queue_lock;