--- zzzz-none-000/linux-3.10.107/include/uapi/mtd/ubi-user.h	2017-06-27 09:49:32.000000000 +0000
+++ vr9-7490-729/linux-3.10.107/include/uapi/mtd/ubi-user.h	2021-11-10 11:53:56.000000000 +0000
@@ -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.
  */
 
 /*
@@ -173,7 +183,10 @@
 
 #define UBI_VOL_IOC_MAGIC 'O'
 
-/* Start UBI volume update */
+/* Start UBI volume update
+ * Note: This actually takes a pointer (__s64*), but we can't change
+ *       that without breaking the ABI on 32bit systems
+ */
 #define UBI_IOCVOLUP _IOW(UBI_VOL_IOC_MAGIC, 0, __s64)
 /* LEB erasure command, used for debugging, disabled by default */
 #define UBI_IOCEBER _IOW(UBI_VOL_IOC_MAGIC, 1, __s32)
@@ -188,6 +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
@@ -417,4 +434,12 @@
 	__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__ */