[flashrom] Where is read lock typically implemented?

[Stefan Tauner]

On Tue, 5 Aug 2014 12:55:33 -0400
TR Reardon <thomas_reardon at hotmail.com> wrote:

> I tried looking for an answer to this but a quick one didn't surface: when
> flash regions are protected, is this implemented by the flash chip itself
> or by the SPI logic (ie ichspi for Intel programmer)?

Both, and more. There are 3 common cases:

1) was used at least in the last 20 years or so: a GPIO line from the
chipset is connected to the write protection pin (most flash chips have
that). This is usually mainboard-specific and is handled by flashrom in
board_enable.c

2) Some flash chips offer software locking mechanisms where some
commands need to be sent to the flash chip to lock and unlock
respective address ranges. Those settings can then also be
hardward-locked via 1)

3) are programmer-based protections such those seen on Intel chipsets
where the chipset hardware implements a kind of firewall for the SPI
stream.

-- 
Kind regards/Mit freundlichen Grüßen, Stefan Tauner