UBI: improve ioctl commentaries

Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

include/mtd/ubi-user.h

@@ -40,37 +40,37 @@
  * UBI volume creation
  * ~~~~~~~~~~~~~~~~~~~
  *
- * UBI volumes are created via the %UBI_IOCMKVOL IOCTL command of UBI character
+ * UBI volumes are created via the %UBI_IOCMKVOL ioctl command of UBI character
  * device. A &struct ubi_mkvol_req object has to be properly filled and a
- * pointer to it has to be passed to the IOCTL.
+ * pointer to it has to be passed to the ioctl.
  *
  * UBI volume deletion
  * ~~~~~~~~~~~~~~~~~~~
  *
- * To delete a volume, the %UBI_IOCRMVOL IOCTL command of the UBI character
+ * To delete a volume, the %UBI_IOCRMVOL ioctl command of the UBI character
  * device should be used. A pointer to the 32-bit volume ID hast to be passed
- * to the IOCTL.
+ * to the ioctl.
  *
  * UBI volume re-size
  * ~~~~~~~~~~~~~~~~~~
  *
- * To re-size a volume, the %UBI_IOCRSVOL IOCTL command of the UBI character
+ * To re-size a volume, the %UBI_IOCRSVOL ioctl command of the UBI character
  * device should be used. A &struct ubi_rsvol_req object has to be properly
- * filled and a pointer to it has to be passed to the IOCTL.
+ * filled and a pointer to it has to be passed to the ioctl.
  *
  * UBI volumes re-name
  * ~~~~~~~~~~~~~~~~~~~
  *
  * To re-name several volumes atomically at one go, the %UBI_IOCRNVOL command
  * of the UBI character device should be used. A &struct ubi_rnvol_req object
- * has to be properly filled and a pointer to it has to be passed to the IOCTL.
+ * has to be properly filled and a pointer to it has to be passed to the ioctl.
  *
  * UBI volume update
  * ~~~~~~~~~~~~~~~~~
  *
- * Volume update should be done via the %UBI_IOCVOLUP IOCTL command of the
+ * Volume update should be done via the %UBI_IOCVOLUP ioctl command of the
  * corresponding UBI volume character device. A pointer to a 64-bit update
- * size should be passed to the IOCTL. After this, UBI expects user to write
+ * size should be passed to the ioctl. After this, UBI expects user to write
  * this number of bytes to the volume character device. The update is finished
  * when the claimed number of bytes is passed. So, the volume update sequence
  * is something like:
@@ -80,14 +80,50 @@
  * write(fd, buf, image_size);
  * close(fd);
  *
- * Atomic eraseblock change
+ * Logical eraseblock erase
  * ~~~~~~~~~~~~~~~~~~~~~~~~
  *
- * Atomic eraseblock change operation is done via the %UBI_IOCEBCH IOCTL
- * command of the corresponding UBI volume character device. A pointer to
- * &struct ubi_leb_change_req has to be passed to the IOCTL. Then the user is
- * expected to write the requested amount of bytes. This is similar to the
- * "volume update" IOCTL.
+ * To erase a logical eraseblock, the %UBI_IOCEBER ioctl command of the
+ * corresponding UBI volume character device should be used. This command
+ * unmaps the requested logical eraseblock, makes sure the corresponding
+ * physical eraseblock is successfully erased, and returns.
+ *
+ * Atomic logical eraseblock change
+ * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ *
+ * Atomic logical eraseblock change operation is called using the %UBI_IOCEBCH
+ * ioctl command of the corresponding UBI volume character device. A pointer to
+ * a &struct ubi_leb_change_req object has to be passed to the ioctl. Then the
+ * user is expected to write the requested amount of bytes (similarly to what
+ * should be done in case of the "volume update" ioctl).
+ *
+ * Logical eraseblock map
+ * ~~~~~~~~~~~~~~~~~~~~~
+ *
+ * To map a logical eraseblock to a physical eraseblock, the %UBI_IOCEBMAP
+ * ioctl command should be used. A pointer to a &struct ubi_map_req object is
+ * expected to be passed. The ioctl maps the requested logical eraseblock to
+ * a physical eraseblock and returns.  Only non-mapped logical eraseblocks can
+ * be mapped. If the logical eraseblock specified in the request is already
+ * mapped to a physical eraseblock, the ioctl fails and returns error.
+ *
+ * Logical eraseblock unmap
+ * ~~~~~~~~~~~~~~~~~~~~~~~~
+ *
+ * To unmap a logical eraseblock to a physical eraseblock, the %UBI_IOCEBUNMAP
+ * ioctl command should be used. The ioctl unmaps the logical eraseblocks,
+ * schedules corresponding physical eraseblock for erasure, and returns. Unlike
+ * the "LEB erase" command, it does not wait for the physical eraseblock being
+ * erased. Note, the side effect of this is that if an unclean reboot happens
+ * after the unmap ioctl returns, you may find the LEB mapped again to the same
+ * physical eraseblock after the UBI is run again.
+ *
+ * Check if logical eraseblock is mapped
+ * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ *
+ * To check if a logical eraseblock is mapped to a physical eraseblock, the
+ * %UBI_IOCEBISMAP ioctl command should be used. It returns %0 if the LEB is
+ * not mapped, and %1 if it is mapped.
  */
 
 /*
@@ -101,7 +137,7 @@
 /* Maximum volume name length */
 #define UBI_MAX_VOLUME_NAME 127
 
-/* IOCTL commands of UBI character devices */
+/* ioctl commands of UBI character devices */
 
 #define UBI_IOC_MAGIC 'o'
 
@@ -114,7 +150,7 @@
 /* Re-name volumes */
 #define UBI_IOCRNVOL _IOW(UBI_IOC_MAGIC, 3, struct ubi_rnvol_req)
 
-/* IOCTL commands of the UBI control character device */
+/* ioctl commands of the UBI control character device */
 
 #define UBI_CTRL_IOC_MAGIC 'o'
 
@@ -123,21 +159,21 @@
 /* Detach an MTD device */
 #define UBI_IOCDET _IOW(UBI_CTRL_IOC_MAGIC, 65, int32_t)
 
-/* IOCTL commands of UBI volume character devices */
+/* ioctl commands of UBI volume character devices */
 
 #define UBI_VOL_IOC_MAGIC 'O'
 
 /* Start UBI volume update */
 #define UBI_IOCVOLUP _IOW(UBI_VOL_IOC_MAGIC, 0, int64_t)
-/* An eraseblock erasure command, used for debugging, disabled by default */
+/* LEB erasure command, used for debugging, disabled by default */
 #define UBI_IOCEBER _IOW(UBI_VOL_IOC_MAGIC, 1, int32_t)
-/* An atomic eraseblock change command */
+/* Atomic LEB change command */
 #define UBI_IOCEBCH _IOW(UBI_VOL_IOC_MAGIC, 2, int32_t)
-/* Map an eraseblock, used for debugging, disabled by default */
+/* Map LEB command */
 #define UBI_IOCEBMAP _IOW(UBI_VOL_IOC_MAGIC, 3, struct ubi_map_req)
-/* Unmap an eraseblock, used for debugging, disabled by default */
+/* Unmap LEB command */
 #define UBI_IOCEBUNMAP _IOW(UBI_VOL_IOC_MAGIC, 4, int32_t)
-/* Check if an eraseblock is mapped, used for debugging, disabled by default */
+/* Check if LEB is mapped command */
 #define UBI_IOCEBISMAP _IOR(UBI_VOL_IOC_MAGIC, 5, int32_t)
 
 /* Maximum MTD device name length supported by UBI */
@@ -311,8 +347,8 @@ struct ubi_rnvol_req {
 } __attribute__ ((packed));
 
 /**
- * struct ubi_leb_change_req - a data structure used in atomic logical
- *                             eraseblock change requests.
+ * struct ubi_leb_change_req - a data structure used in atomic LEB change
+ *                             requests.
  * @lnum: logical eraseblock number to change
  * @bytes: how many bytes will be written to the logical eraseblock
  * @dtype: data type (%UBI_LONGTERM, %UBI_SHORTTERM, %UBI_UNKNOWN)
@@ -326,7 +362,7 @@ struct ubi_leb_change_req {
 } __attribute__ ((packed));
 
 /**
- * struct ubi_map_req - a data structure used in map eraseblock requests.
+ * struct ubi_map_req - a data structure used in map LEB requests.
  * @lnum: logical eraseblock number to unmap
  * @dtype: data type (%UBI_LONGTERM, %UBI_SHORTTERM, %UBI_UNKNOWN)
  * @padding: reserved for future, not used, has to be zeroed