This pull request includes the 'ubiblock' driver which provides R/O block

access to UBI volumes. It is useful for those who want to use squashfs on top
 of raw flash devices. UBI will provide bit-flip handling and wear-levelling in
 this case (e.g., if there are other UBI volumes with R/W UBIFS too).
 
 The driver is actually pretty small and it is part of the UBI kernel subsystem.
 Delivered by Ezequiel Garcia, along with a piece of documentation on the MTD
 web site and the user-space tool for creating and removing block devices.
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Merge tag 'upstream-3.15-rc1' of git://git.infradead.org/linux-ubifs

Pull ubifs updates from Artem Bityutskiy:
 "This pull request includes the 'ubiblock' driver which provides R/O
  block access to UBI volumes.  It is useful for those who want to use
  squashfs on top of raw flash devices.  UBI will provide bit-flip
  handling and wear-levelling in this case (e.g., if there are other UBI
  volumes with R/W UBIFS too).

  The driver is actually pretty small and it is part of the UBI kernel
  subsystem.  Delivered by Ezequiel Garcia, along with a piece of
  documentation on the MTD web site and the user-space tool for creating
  and removing block devices"

* tag 'upstream-3.15-rc1' of git://git.infradead.org/linux-ubifs:
  UBI: block: Remove __initdata from ubiblock_param_ops
  UBI: make UBI_IOCVOLCRBLK take a parameter for future usage
  UBI: rename block device ioctls
  UBI: block: Use ENOSYS as return value when CONFIG_UBIBLOCK=n
  UBI: block: Add CONFIG_BLOCK dependency
  UBI: block: Use 'u64' for the 64-bit dividend
  UBI: block: Mark init-only symbol as __initdata
  UBI: block: do not use term "attach"
  UBI: R/O block driver on top of UBI volumes

include/uapi/mtd/ubi-user.h

@@ -134,6 +134,16 @@
  * used. A pointer to a &struct ubi_set_vol_prop_req object is expected to be
  * passed. The object describes which property should be set, and to which value
  * it should be set.
+ *
+ * Block devices on UBI volumes
+ * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ *
+ * To create a R/O block device on top of an UBI volume the %UBI_IOCVOLCRBLK
+ * should be used. A pointer to a &struct ubi_blkcreate_req object is expected
+ * to be passed, which is not used and reserved for future usage.
+ *
+ * Conversely, to remove a block device the %UBI_IOCVOLRMBLK should be used,
+ * which takes no arguments.
  */
 
 /*
@@ -191,6 +201,10 @@
 /* Set an UBI volume property */
 #define UBI_IOCSETVOLPROP _IOW(UBI_VOL_IOC_MAGIC, 6, \
 			       struct ubi_set_vol_prop_req)
+/* Create a R/O block device on top of an UBI volume */
+#define UBI_IOCVOLCRBLK _IOW(UBI_VOL_IOC_MAGIC, 7, struct ubi_blkcreate_req)
+/* Remove the R/O block device */
+#define UBI_IOCVOLRMBLK _IO(UBI_VOL_IOC_MAGIC, 8)
 
 /* Maximum MTD device name length supported by UBI */
 #define MAX_UBI_MTD_NAME_LEN 127
@@ -420,4 +434,12 @@ struct ubi_set_vol_prop_req {
 	__u64 value;
 }  __packed;
 
+/**
+ * struct ubi_blkcreate_req - a data structure used in block creation requests.
+ * @padding: reserved for future, not used, has to be zeroed
+ */
+struct ubi_blkcreate_req {
+	__s8  padding[128];
+}  __packed;
+
 #endif /* __UBI_USER_H__ */