[cip-dev][isar-cip-core][RFC 4/5] image_uuid: read target_image_uuid

[Quirin Gylstorff <Quirin.Gylstorff@siemens.com>]

From: Quirin Gylstorff <quirin.gylstorff@siemens.com>

This writes the target_image_uuid to the Variable TARGET_IMAGE_UUID
which can be used to validate a update against the root file system.

Signed-off-by: Quirin Gylstorff <quirin.gylstorff@siemens.com>
---
 classes/image_uuid.bbclass | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/classes/image_uuid.bbclass b/classes/image_uuid.bbclass
index 277941b..3e2e3de 100644
--- a/classes/image_uuid.bbclass
+++ b/classes/image_uuid.bbclass
@@ -13,6 +13,8 @@
 inherit rootfs
 inherit image
 
+# Generate the uuid from BB_TASKHASH to ensure a new
+# hash on each rebuild
 def generate_image_uuid(d):
     import uuid
 
@@ -23,6 +25,23 @@ def generate_image_uuid(d):
 
 IMAGE_UUID ?= "${@generate_image_uuid(d)}"
 
+def read_target_image_uuid(d):
+    import os.path
+
+    deploy_dir = d.getVar("DEPLOY_DIR_IMAGE")
+    image_full_name = d.getVar("IMAGE_FULLNAME")
+    uuid_file = f"{deploy_dir}/{image_full_name}.uuid.env"
+    if not os.path.isfile(uuid_file):
+        return None
+
+    target_image_uuid = None
+    with open(uuid_file, "r") as f:
+       uuid_file_content = f.read()
+       target_image_uuid = uuid_file_content.split('=')[1].strip(' \t\n\r').strip('\"')
+    return target_image_uuid
+
+TARGET_IMAGE_UUID = "${@read_target_image_uuid(d)}"
+
 do_generate_image_uuid[vardeps] += "IMAGE_UUID"
 do_generate_image_uuid[depends] = "buildchroot-target:do_build"
 do_generate_image_uuid[dirs] = "${DEPLOY_DIR_IMAGE}"
-- 
2.35.1