Partition sizing

You must configure the partition size for the LittleFS backend to accommodate the data types in use, their sizes, and the number of records per type. A minimum partition size is required to ensure proper operation.

How to calculate the needed size:

• Per-type block need:

blocks per type=⌈data size×records per typeblock size⌉ \text{blocks per type} = \left\lceil \frac{\text{data size} \times \text{records per type}}{\text{block size}} \right\rceil

• Total required blocks:

required blocks=∑blocks per type+3 \text{required blocks} = \sum \text{blocks per type} + 3

where the +3 accounts for LittleFS metadata and the CoW block.

• Minimum partition size:

flash size=required blocks×block size \text{flash size} = \text{required blocks} \times \text{block size}

Choose a partition size that meets or exceeds flash_size. The LittleFS partition size is set by the littlefs_storage node in app/boards/att_flash_partitions.dtsi, which both board overlays include:

littlefs_storage: partition@4d2000 {
    label = "littlefs_storage";
    reg = <0x004d2000 0x00100000>;   /* 1 MiB */
};

The second reg cell (0x00100000 above) is the partition size in bytes. To make the partition larger, raise that value and shrink the adjacent external_flash_partition by the same amount so the 32 MiB external flash layout stays consistent.

If the requirement is not met, either grow the partition in att_flash_partitions.dtsi as shown above, or reduce storage pressure (fewer records, smaller data types, or fewer enabled types).