From b36b1e4213adb83fef48b955c3b0612ee33066c7 Mon Sep 17 00:00:00 2001 From: James Hughes Date: Tue, 25 Feb 2020 10:07:19 +0000 Subject: [PATCH] OTP read disable Added paragraph on how to make customer OTP unreadable. --- hardware/industrial/README.md | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff --git a/hardware/industrial/README.md b/hardware/industrial/README.md index 4b2d411a2..bc2229e72 100644 --- a/hardware/industrial/README.md +++ b/hardware/industrial/README.md @@ -63,4 +63,14 @@ It is possible to lock the OTP changes to avoid them being edited again. This ca pi@raspberrypi:~ $ /opt/vc/bin/vcmailbox 0x00038021 8 8 0xffffffff 0xaffe0000 ``` -Once locked, none of the customer OTP values can be accessed. +Once locked, the customer OTP values can no longer be altered. Note that this locking operation is irreversible. + +## Making Customer OTP bits unreadable + +It is possible to prevent the customer OTP bits from being read at all. This can be done using a special argument with the OTP write mailbox: + +``` +pi@raspberrypi:~ $ /opt/vc/bin/vcmailbox 0x00038021 8 8 0xffffffff 0xaffebabe +``` + + This operation is unlikely to be useful for the vast majority of users, and is irreversible.