autoboot: Improve docs for CONFIG_AUTOBOOT_ENCRYPTION

[oweals/u-boot.git] / doc / README.autoboot

diff --git a/doc/README.autoboot b/doc/README.autoboot
index eeb7e4c66235163d33372f60307a925679a6a119..de35f3093df0156f0eb2cb467eae427cc4606fef 100644 (file)
--- a/doc/README.autoboot
+++ b/doc/README.autoboot
@@ -132,6 +132,21 @@ What they do
        provides an escape sequence from the limited "password"
        strings.
 
+  CONFIG_AUTOBOOT_ENCRYPTION
+
+  "bootstopkeysha256"  environment variable
+
+       - Hash value of the input which unlocks the device and
+         stops autoboot.
+
+       This option allows a string to be entered into U-Boot to stop the
+       autoboot. The string itself is hashed and compared against the hash
+       in the environment variable 'bootstopkeysha256'. If it matches then
+       boot stops and a command-line prompt is presented.
+
+       This provides a way to ship a secure production device which can also
+       be accessed at the U-Boot command line.
+
   CONFIG_RESET_TO_RETRY
 
        (Only effective when CONFIG_BOOT_RETRY_TIME is also set)