[flashrom] Emulating a flash chip for a real device
a.nielsen at shikadi.net
Sat Mar 16 22:15:39 CET 2013
I have just purchased a network-connected video camera which runs Linux, and I
would like to experiment with creating my own firmware for it. Since I am
likely to brick the device a few times with this, I'd like to come up with a
way of recovering it before I start.
The firmware (bootloader + kernel) is stored inside a 4MB SPI flash chip
supported by flashrom, however it is soldered onto the board, so presumably to
reflash it I will have to desolder at least one of the pins to avoid the
flashrom commands getting tangled up with those sent by the device itself when
reading the chip.
However I was thinking that instead of reflashing the entire chip every time
something goes wrong, it would be a lot easier if I could produce my firmware
image as a 4MB file, and emulate the chip so that the file is accessed
directly every time the camera tries to read from the flash chip.
I see flashrom can already emulate some chips with the 'dummy' programmer, and
as most (all?) programmers can both read and write data I am wondering whether
it is possible to set flashrom up as a virtual flash chip connected to a real
circuit, responding to read and write commands received from other chips in
I plan to use a Bus Pirate as a programmer, so if I remove the flash chip and
connect the Bus Pirate to the circuit instead, being able to edit a file and
reset the device without actually reflashing anything would be a huge time saver.
If this isn't currently possible, would it be a big job to add support for it?
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