diff options
Diffstat (limited to 'include/mtd/ubi-header.h')
| -rw-r--r-- | include/mtd/ubi-header.h | 43 |
1 files changed, 41 insertions, 2 deletions
diff --git a/include/mtd/ubi-header.h b/include/mtd/ubi-header.h index 74efa776347..69d5d7e2289 100644 --- a/include/mtd/ubi-header.h +++ b/include/mtd/ubi-header.h @@ -58,6 +58,43 @@ enum { }; /* + * Volume flags used in the volume table record. + * + * @UBI_VTBL_AUTORESIZE_FLG: auto-resize this volume + * + * %UBI_VTBL_AUTORESIZE_FLG flag can be set only for one volume in the volume + * table. UBI automatically re-sizes the volume which has this flag and makes + * the volume to be of largest possible size. This means that if after the + * initialization UBI finds out that there are available physical eraseblocks + * present on the device, it automatically appends all of them to the volume + * (the physical eraseblocks reserved for bad eraseblocks handling and other + * reserved physical eraseblocks are not taken). So, if there is a volume with + * the %UBI_VTBL_AUTORESIZE_FLG flag set, the amount of available logical + * eraseblocks will be zero after UBI is loaded, because all of them will be + * reserved for this volume. Note, the %UBI_VTBL_AUTORESIZE_FLG bit is cleared + * after the volume had been initialized. + * + * The auto-resize feature is useful for device production purposes. For + * example, different NAND flash chips may have different amount of initial bad + * eraseblocks, depending of particular chip instance. Manufacturers of NAND + * chips usually guarantee that the amount of initial bad eraseblocks does not + * exceed certain percent, e.g. 2%. When one creates an UBI image which will be + * flashed to the end devices in production, he does not know the exact amount + * of good physical eraseblocks the NAND chip on the device will have, but this + * number is required to calculate the volume sized and put them to the volume + * table of the UBI image. In this case, one of the volumes (e.g., the one + * which will store the root file system) is marked as "auto-resizable", and + * UBI will adjust its size on the first boot if needed. + * + * Note, first UBI reserves some amount of physical eraseblocks for bad + * eraseblock handling, and then re-sizes the volume, not vice-versa. This + * means that the pool of reserved physical eraseblocks will always be present. + */ +enum { + UBI_VTBL_AUTORESIZE_FLG = 0x01, +}; + +/* * Compatibility constants used by internal volumes. * * @UBI_COMPAT_DELETE: delete this internal volume before anything is written @@ -289,7 +326,8 @@ struct ubi_vid_hdr { * @upd_marker: if volume update was started but not finished * @name_len: volume name length * @name: the volume name - * @padding2: reserved, zeroes + * @flags: volume flags (%UBI_VTBL_AUTORESIZE_FLG) + * @padding: reserved, zeroes * @crc: a CRC32 checksum of the record * * The volume table records are stored in the volume table, which is stored in @@ -324,7 +362,8 @@ struct ubi_vtbl_record { __u8 upd_marker; __be16 name_len; __u8 name[UBI_VOL_NAME_MAX+1]; - __u8 padding2[24]; + __u8 flags; + __u8 padding[23]; __be32 crc; } __attribute__ ((packed)); |