kconfig: allow specifying the seed for randconfig

For reproducibility, it can be useful to be able to specify the
seed to use to seed the RNG.

Add a new KCONFIG_SEED environment variable which can be set to
the seed to use:
    $ make KCONFIG_SEED=42 randconfig
    $ sha1sum .config
    70a128c8dcc61303069e1be352cce64114dfcbca  .config
    $ make KCONFIG_SEED=42 randconfig
    $ sha1sum .config
    70a128c8dcc61303069e1be352cce64114dfcbca  .config

It's very usefull for eg. debugging the kconfig parser.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>

1 files changed, 9 insertions, 0 deletions

diff --git a/Documentation/kbuild/kconfig.txt b/Documentation/kbuild/kconfig.txt
index b8b77bbc784f..dbf746b70553 100644
--- a/Documentation/kbuild/kconfig.txt
+++ b/Documentation/kbuild/kconfig.txt
@@ -90,6 +90,15 @@ disable the options that are explicitly listed in the specified
 mini-config files.
 
 ______________________________________________________________________
+Environment variables for 'randconfig'
+
+KCONFIG_SEED
+--------------------------------------------------
+You can set this to the integer value used to seed the RNG, if you want
+to somehow debug the behaviour of the kconfig parser/frontends.
+If not set, the current time will be used.
+
+______________________________________________________________________
 Environment variables for 'silentoldconfig'
 
 KCONFIG_NOSILENTUPDATE