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knc1 · 06-23-2012, 01:58 PM

One theory occurred to me today while answering another post...

The eMMC, like other flash based devices, does not "write".
It "reads, merges, erases, and re-programs".

I have not examined my own kindle or the firmware images (yet), but...

The "power off" command of *nix is often associated with the "reboot" command. (Highly implementation Dependant.)

For non-flash based systems, "reboot" will typically flush (sync) the VFS file buffers followed by un-mounting the file systems (among other things).

Both the "sync" and the "umount" (normally) are blocking events.
BUT in the case of flash media, the "writes" generated will all return before the micro-controller finishes its sequence on each erase block involved.

Then if "power off" is implemented to actually remove power from the electronics (or at least from the eMMC)...

Then it would be possible to remove power before the micro-controller finishes.
This is one, certain, way to corrupt the flash media internally.

When, if ever, we get this unit restored to operation, it would be nice to learn exactly how it was damaged.
But so far it does read like internal corruption of the flash media.

06-23-2012, 01:58 PM	#63
knc1 Going Viral Posts: 17,212 Karma: 18210809 Join Date: Feb 2012 Location: Central Texas Device: No K1, PW2, KV, KOA	How? One theory occurred to me today while answering another post... The eMMC, like other flash based devices, does not "write". It "reads, merges, erases, and re-programs". I have not examined my own kindle or the firmware images (yet), but... The "power off" command of nix is often associated with the "reboot" command. (Highly implementation Dependant.) For non-flash based systems, "reboot" will typically flush (sync) the VFS file buffers followed by un-mounting the file systems (among other things). Both the "sync" and the "umount" (normally) are blocking events. BUT* in the case of flash media, the "writes" generated will all return before the micro-controller finishes its sequence on each erase block involved. Then if "power off" is implemented to actually remove power from the electronics (or at least from the eMMC)... Then it would be possible to remove power before the micro-controller finishes. This is one, certain, way to corrupt the flash media internally. When, if ever, we get this unit restored to operation, it would be nice to learn exactly how it was damaged. But so far it does read like internal corruption of the flash media.