[ptxdist] [PATCH 3/3] doc: ref: document config hash macros and variables

[Roland Hieber <rhi@pengutronix.de>]

Signed-off-by: Roland Hieber <rhi@pengutronix.de>
---
 doc/ref_make_macros.rst    | 18 ++++++++++++++++++
 doc/ref_make_variables.rst |  9 +++++++++
 2 files changed, 27 insertions(+)

diff --git a/doc/ref_make_macros.rst b/doc/ref_make_macros.rst
index 4c1ca2f0375f..3ea331baee4b 100644
--- a/doc/ref_make_macros.rst
+++ b/doc/ref_make_macros.rst
@@ -681,6 +681,24 @@ be installed with some other ``install_*`` command before
    	@$(call install_replace, timezone, /etc/timezone, @TIMEZONE@, \
    		$(PTXCONF_TIMEZONE_LOCALTIME))
 
+.. _ptx/cfghash:
+.. _ptx/cfghash-file:
+
+ptx/cfghash, ptx/cfghash-file
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Usage:
+
+.. code-block:: make
+
+ $(call ptx/cfghash, <PKG>, <string>)
+ $(call ptx/cfghash-file, <PKG>, <file>)
+
+Add an arbitrary **<string>** or the content of **<file>** to the config hash
+for **<PKG>**.
+This has the effect that the package will be rebuilt when the string or the
+content of the file changes.
+
 .. _param_macros:
 .. _ptxEndis:
 .. _ptxDisen:
diff --git a/doc/ref_make_variables.rst b/doc/ref_make_variables.rst
index beca984edccc..7ec09cbb3e91 100644
--- a/doc/ref_make_variables.rst
+++ b/doc/ref_make_variables.rst
@@ -345,6 +345,15 @@ Build Environment for all Stages
 Prepare Stage
 ^^^^^^^^^^^^^
 
+``<PKG>_CFGHASH``
+  This variable contains the config hash for the package.
+  If it changes, PTXdist rebuilds the prepare stage of the package (and
+  successively, all following stages).
+
+  You should not need to touch this variable directly.
+  To add content to the config hash, you can use the macros :ref:`ptx/cfghash
+  and ptx/cfghash-file <ptx/cfghash>`.
+
 ``<PKG>_CONF_ENV``
   The environment for the prepare stage. If undefined, PTXdist will use
   ``$(CROSS_ENV)`` for target packages, ``$(HOST_ENV)`` for host packages
-- 
2.30.2