ubi: Expose interface for detailed erase counters

Using the ioctl command 'UBI_IOCECNFO' user space can obtain
detailed erase counter information of all blocks of a device.

Signed-off-by: Rickard Andersson <rickard.andersson@axis.com>
Reviewed-by: Zhihao Cheng <chengzhihao1@huawei.com>
Signed-off-by: Richard Weinberger <richard@nod.at>

Author: Rickard Andersson

include/uapi/mtd/ubi-user.h

@@ -175,6 +175,8 @@
 #define UBI_IOCRPEB _IOW(UBI_IOC_MAGIC, 4, __s32)
 /* Force scrubbing on the specified PEB */
 #define UBI_IOCSPEB _IOW(UBI_IOC_MAGIC, 5, __s32)
+/* Read detailed device erase counter information */
+#define UBI_IOCECNFO _IOWR(UBI_IOC_MAGIC, 6, struct ubi_ecinfo_req)
 
 /* ioctl commands of the UBI control character device */
 
@@ -412,6 +414,37 @@ struct ubi_rnvol_req {
 	} ents[UBI_MAX_RNVOL];
 } __packed;
 
+/**
+ * struct ubi_ecinfo_req - a data structure used for requesting and receiving
+ * erase block counter information from a UBI device.
+ *
+ * @start: index of first physical erase block to read (in)
+ * @length: number of erase counters to read (in)
+ * @read_length: number of erase counters that was actually read (out)
+ * @padding: reserved for future, not used, has to be zeroed
+ * @erase_counters: array of erase counter values (out)
+ *
+ * This structure is used to retrieve erase counter information for a specified
+ * range of PEBs on a UBI device.
+ * Erase counters are read from @start and attempts to read @length number of
+ * erase counters.
+ * The retrieved values are stored in the @erase_counters array. It is the
+ * responsibility of the caller to allocate enough memory for storing @length
+ * elements in the @erase_counters array.
+ * If a block is bad or if the erase counter is unknown the corresponding value
+ * in the array will be set to -1.
+ * The @read_length field will indicate the number of erase counters actually
+ * read. Typically @read_length will be limited due to memory or the number of
+ * PEBs on the UBI device.
+ */
+struct ubi_ecinfo_req {
+	__s32 start;
+	__s32 length;
+	__s32 read_length;
+	__s8  padding[16];
+	__s32 erase_counters[];
+}  __packed;
+
 /**
  * struct ubi_leb_change_req - a data structure used in atomic LEB change
  *                             requests.