nuttx/Documentation/components/filesystem/partition.rst

===============
Partition Table
===============

Text based Partition Table
==========================

**Summary**

TXTABLE - A text based partition table stored in last eraseblock
(or in romdisk for backup).

1. The 1st line must be "Magic+Version", current is "TXTABLE0".
#. The 2nd and remaining lines are partition entries(min: one)
   in format: "%s %zx %zx"(means name, size and offset (byte)(in hex)).
#. Size or offset can be default zero(means zero(for 1st entry) or
   calculated(for others)), and will be calculated by the parser refs to previous
   and next entries.
#. The last eraseblock will be registered as pseudo partition named "txtable".
   If the last eraseblock included by the last real partition, it will be
   excluded from.

To avoid problems of PTABLE: In case of multiple NuttX binary,
partition table maybe out of sync.

And it's easier:

1. Text format with simple rules(name + size + offset).
#. Size or offset can be default(calculated refs to previous
   and next entries).
#. Support backup table(eg. /etc/txtable.txt in ROMFS)

Size / Offset can be automatically calculated, case:

1. The offset of the first entry is zero, and the offset of other entries
   is zero: automatic calculation;
#. The size of the last entry is zero: fill to the end of the entire Flash
   (keep the last eraseblock); the size of other entries is zero:
   automatically calculated(next.offset - current.offset);
#. Typical case 1: The size of all entries is
   zero (calculated automatically), and the offset is non-zero;
#. Typical case 2: The size and offset of a certain entry are all zero,
   but the size and offset of two adjacent entries are all non-zero;

**Examples**

Both size and offset of "partition6" are zero,
gap exists between "partition7" and "data",
and not reserve last eraseblock.

* txtable.txt

  ::

    TXTABLE0
    partition1 0x6C000 0x4000
    partition2 0x10000 0x70000
    partition3 0x80000 0x80000
    partition4 0x80000 0x100000
    partition5 0x280000 0x180000
    partition6 0 0
    partition7 0x10000 0x480000
    data 0 0x500000



* Parsed

  | Reserved last eraseblock, and gap between partition7 and data is kept.
  | Format: name, offset, size

  ::

    /dev/partition1   offset 0x00004000, size 0x0006c000
    /dev/partition2   offset 0x00070000, size 0x00010000
    /dev/partition3   offset 0x00080000, size 0x00080000
    /dev/partition4   offset 0x00100000, size 0x00080000
    /dev/partition5   offset 0x00180000, size 0x00280000
    /dev/partition6   offset 0x00400000, size 0x00080000
    /dev/partition7   offset 0x00480000, size 0x00010000
    /dev/data         offset 0x00500000, size 0x00aff000
    /dev/txtable      offset 0x00fff000, size 0x00001000

More than one not set size or offset

* txtable.txt

  ::

    TXTABLE0
    partition1 0 0x4000
    partition2 0 0x70000
    partition3 0 0x80000
    partition4 0x80000 0x100000
    partition5 0x280000 0
    partition6 0 0
    partition7 0x10000 0x480000
    data 0 0x500000

* Parsed

  | Size of partition[2,3,4,6] and data are calculated, and gap between
    partition7 and data is kept.

  ::

    /dev/partition1   offset 0x00004000, size 0x0006c000
    /dev/partition2   offset 0x00070000, size 0x00010000
    /dev/partition3   offset 0x00080000, size 0x00080000
    /dev/partition4   offset 0x00100000, size 0x00080000
    /dev/partition5   offset 0x00180000, size 0x00280000
    /dev/partition6   offset 0x00400000, size 0x00080000
    /dev/partition7   offset 0x00480000, size 0x00010000
    /dev/data         offset 0x00500000, size 0x00aff000
    /dev/txtable      offset 0x00fff000, size 0x00001000

Only one partition entry, and size not spec

* txtable.txt

  ::

    TXTABLE0
    partition1 0x0 0x4000

* Parsed

  | The last eraseblock was kept, and size is correct.

  ::

    /dev/partition1   offset 0x00004000, size 0x00ffb000
    /dev/txtable      offset 0x00fff000, size 0x00001000

Blank line && New line delim

* txtable.txt

  | New line: CR + LF / LF.
  | Additional char/string after "%s %zx %zx".

  ::

    TXTABLE0
    partition1 0x6C000 0x4000
    partition2 0 0x70000
    partition3 0 0x80000
    partition4 0 0x100000
    partition5 0x280000 0x180000
    partition6 0x80000 0x400000   # String between "%s %zx %zx" and "LF" will be ignored.
    partition7 0x10000 0x480000   # Comments: This is the 7th partition.
    data 0 0x500000
    
    
    
    EOF

* Parsed

  | Blank lines are ignored, and new line of both "LF" or "CRLF" are parsed.
    String between "%s %zx %zx" and "LF" will be ignored(eg. CR, or some comments).

  ::

    /dev/partition1   offset 0x00004000, size 0x0006c000
    /dev/partition2   offset 0x00070000, size 0x00010000
    /dev/partition3   offset 0x00080000, size 0x00080000
    /dev/partition4   offset 0x00100000, size 0x00080000
    /dev/partition5   offset 0x00180000, size 0x00280000
    /dev/partition6   offset 0x00400000, size 0x00080000
    /dev/partition7   offset 0x00480000, size 0x00010000
    /dev/data         offset 0x00500000, size 0x00aff000
    /dev/txtable      offset 0x00fff000, size 0x00001000