Broadcom BCM47xx Partitions
Broadcom is one of hardware manufacturers providing SoCs (BCM47xx) used in
home routers. Their BCM947xx boards using CFE bootloader have several partitions
without any on-flash partition table. On some devices their sizes and/or
meanings can also vary so fixed partitioning can’t be used.
Discovering partitions on these devices is possible thanks to having a special
header and/or magic signature at the beginning of each of them. They are also
block aligned which is important for determinig a size.
Most of partitions use ASCII text based magic for determining a type. More
complex partitions (like TRX with its HDR0 magic) may include extra header
containing some details, including a length.
A list of supported partitions includes:
- Bootloader with Broadcom’s CFE (Common Firmware Environment)
- NVRAM with configuration/calibration data
- Device manufacturer’s data with some default values (e.g. SSIDs)
- TRX firmware container which can hold up to 4 subpartitions
- Backup TRX firmware used after failed upgrade
As mentioned earlier, role of some partitions may depend on extra configuration.
For example both: main firmware and backup firmware use the same TRX format with
the same header. To distinguish currently used firmware a CFE’s environment
variable “bootpartition” is used.
Devices using Broadcom partitions described above should should have flash node
with a subnode named “partitions” using following properties:
Required properties:
- compatible : (required) must be “brcm,bcm947xx-cfe-partitions”
Example:
flash@0 {
partitions {
compatible = “brcm,bcm947xx-cfe-partitions”;
};
};
