--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mysteryffs/README	Sat May 18 08:22:15 2013 +0000
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+MysteryFFS is my (Michael Spacefalcon's) arbitrarily-chosen nickname for the
+flash file system found in at least two Calypso/Riviera-based GSM phone or
+modem SW designs: Pirelli DP-L10 and Closedmoko GTA0x.
+
+The FFS implementation which I have nicknamed MysteryFFS is identifiable by the
+following magic at the beginning of every flash erase unit used by this FFS:
+
+00000000:  46 66 73 23 10 02 FF FF  AB FF FF FF FF FF FF FF  Ffs#............
+
+The byte at offset 8 into the erase unit (AB in the illustration above)
+has been observed to be one of 3 possibilities:
+
+AB:	this erase unit appears to be the active index block
+BD:	regular data block
+BF:	last block of the flash "partition" used for the FFS
+
+On the Pirelli this MysteryFFS takes up the first 4.5 MiB (18 erase units
+of 256 KiB each) of the 2nd flash chip select (nCS3).  On the Closedmoko
+it lives in the second half of the last megabyte of the 4 MiB flash chip,
+taking up 7 erase units of 64 KiB each, i.e., spanning absolute flash chip
+offsets from 0x380000 through 0x3EFFFF.
+
+(The 4 MiB NOR flash chip used by Closedmoko has an independent R/W bank
+ division between the first 3 MiB and the last 1 MiB.  The first 3 MiB are used
+ to hold the field-flashable closed firmware images distributed as *.m0 files;
+ the independent last megabyte holds the FFS, and thus the FW could be
+ implemented to do FFS writes while running from flash in the main bank.
+ Less than half of that last megabyte appears to be used for the FFS though;
+ the rest appears to be unused - blank flash observed.)
+
+I have nicknamed this flash file system MysteryFFS because I haven't been able
+to identify it as any known FFS design.  The FFS implemented in the liberated
+TSM30 code appears to be different, hence that source is not of much help.
+Therefore, I am reverse-engineering this MysteryFFS in order to extract the
+file system content from my Pirelli phones and from my GTA02.