path: root/include/mtd
diff options
authorArtem Bityutskiy <Artem.Bityutskiy@nokia.com>2008-01-16 15:44:24 +0200
committerArtem Bityutskiy <Artem.Bityutskiy@nokia.com>2008-01-25 16:41:24 +0200
commit4ccf8cffa963c7b5bdc6d455ea9417084ee49aa8 (patch)
treea7281874dc9298b3d7eca2d1e4cb22c326625382 /include/mtd
parentUBI: use bit-fields (diff)
UBI: add auto-resize feature
The problem: NAND flashes have different amount of initial bad physical eraseblocks (marked as bad by the manufacturer). For example, for 256MiB Samsung OneNAND flash there might be from 0 to 40 bad initial eraseblocks, which is about 2%. When UBI is used as the base system, one needs to know the exact amount of good physical eraseblocks, because this number is needed to create the UBI image which is put to the devices during production. But this number is not know, which forces us to use the minimum number of good physical eraseblocks. And UBI additionally reserves some percentage of physical eraseblocks for bad block handling (default is 1%), so we have 1-3% of PEBs reserved at the end, depending on the amount of initial bad PEBs. But it is desired to always have 1% (or more, depending on the configuration). Solution: this patch adds an "auto-resize" flag to the volume table. The volume which has the "auto-resize" flag will automatically be re-sized (enlarged) on the first UBI initialization. UBI clears the flag when the volume is re-sized. Only one volume may have the "auto-resize" flag. So, the production UBI image may have one volume with "auto-resize" flag set, and its size is automatically adjusted on the first boot of the device. Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Diffstat (limited to 'include/mtd')
1 files changed, 41 insertions, 2 deletions
diff --git a/include/mtd/ubi-header.h b/include/mtd/ubi-header.h
index 74efa7763479..69d5d7e22899 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 {
* 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));