• Storage for the environment to support a second stage boot loader (e.g. APEX).

• Storage for the proprietary Intel NPE microcode, which is provided to the open source IXP NPE driver.

The existence of the RedBoot FIS directory is determined by looking of the null-terminated string "RedBoot" at locations 0x507E0000, 0x507E0100, or 0x507E0200. This enables the RedBoot MTD map parser to identify a valid RedBoot FIS directory. SlugImage restricts the size of the FIS directory to a maximum of 15 entries (plus the terminator entry).

We were also intending to use this area for storage of the memory size (for FatSlug support), and kernel command line arguments. Unfortunately, it is not possible to read from the flash memory before the kernel initialises the memory subsystem and parses the kernel command line arguments. So these plans have had to be dropped.

The existence of the RedBoot FIS directory is determined by looking of the null-terminated string "RedBoot" at locations 0x507E0000, 0x507E0100, or 0x507E0200. This enables the RedBoot MTD map parser to identify a valid RedBoot FIS directory. SlugImage restricts the size of the FIS directory to a maximum of 15 entries (plus the terminator entry, which is overlayed with other information).

The existence of the 'sLuGmK' denotes valid additional information in the last block (in particular, the SwitchBox parameter area, and the payload storage area). If the 'sLuGmK' is not present, then the other information cannot be assumed to be valid, and must not be used.

Because it has to be there anyway, we have decided to use it for a couple of other things too:

• Main/Switchbox boot preferences

To enable these uses, we have to modify the SwitchBox linuxrc to deploy the payload, and act upon the boot preferences.

The existence of the 'sLuGmArK' denotes valid additional information in the last block (in particular, the SwitchBox parameter area, and the payload storage area). If the 'sLuGmArK' is not present, then the other information cannot be assumed to be valid, and must not be used.

Historical Info:

We were intending to use this area for storage of the memory size (for http://www.nslu2-linux.org/wiki/HowTo/FattenYourSlug FatSlug support), and kernel command line arguments. Unfortunately, it is not possible to read from the flash memory before the kernel initialises the memory subsystem and parses the kernel command line arguments. So these plans have had to be dropped.

• memory size (for http://www.nslu2-linux.org/wiki/HowTo/FattenYourSlug FatSlug support)

The existence of the 'sLuGmArK' denotes valid additional information in the last block (in particular, the information directly after the FIS directory terminator, the kernel command line args, the payload storage area, and the SwitchBox parameter area). If the 'sLuGmArK' is not present, then the other information cannot be assumed to be valid, and must not be used.

The existence of the 'sLuGmArK' denotes denotes valid additional information in the last block (in particular, the information directly after the FIS directory terminator, the kernel command line args, the payload storage area, and the SwitchBox parameter area). If the 'sLuGmArK' is not present, then the other information cannot be assumed to be valid, and must not be used.

• a payload area for storing kernel modules used by the SwitchBox initial ramdisk

The existence of the 'sLuGmArK' denotes denotes valid additional information in the last block (in particular, the information directly after the FIS directory terminator, the kernel command line args, the payload storage area, and the SwitchBox parameter area). If the 'sLuGmArK' is not present, then the other information cannot be assumed to be present.

To enable these uses, we would have to modify the nslu2 arch-specific kernel files to read stuff from the last block, and modify the SwitchBox linuxrc to deploy the payload.

SlugImage has been upgraded to support the payload already - other additions will come as they are prototyped and proven to work.

The existence of the RedBoot FIS directory is determined by looking of the null-terminated string "RedBoot" at locations 0x507E0000, 0x507E0100, or 0x507E0200. This enables the RedBoot MTD map parser to identify a valid RedBoot FIS directory. SlugImage? restricts the size of the FIS directory to a maximum of 15 entries (plus the terminator entry, which is overlayed with other information).

The existence of the 'sLuGmArK' denotes denotes valid additional information in the last block (in particular, the information directly after the FIS directory terminator, the kernel command line args, the payload storage area, and the SwitchBox parameter area).

• a payload area for storing kernel modules used by the SwitchBox? initial ramdisk

To enable these uses, we would have to modify the nslu2 arch-specific kernel files to read stuff from the last block, and modify the SwitchBox? linuxrc to deploy the payload.

SlugImage? has been upgraded to support the payload already - other additions will come as they are prototyped and proven to work.

• memory size (for FatSlug? support)

To enable these uses, we would have to modify the nslu2 arch-specific kernel files to read stuff from the last block.

• memory size (for FatSlugs?)

• It holds the 16 byte SercommFlashTrailer which is checked by the Redboot boot script commands.

Because it has to be there anyway, we have decided to use it for a number of other things too:

• kernel command arguments
• boot preferences (only if they can't be expressed as kernel command arguments)

We need a tool which can modify the contents of this block without disturbing anything else in the block.

The last erase block in the internal flash memory has a number of dedicated uses:

• It holds the RedBoot FIS directory, which is read by the kernel to define the MTD partitions.
• It holds the 16 byte SerComm Trailer which is checked by the Redboot boot script commands.

• It holds the 16 byte SercommFlashTrailer which is checked by the Redboot boot script commands.