From 01deda9783fbd916eaf46d99757b9506465590b3 Mon Sep 17 00:00:00 2001
From: Austin Bozowski <bozowski@google.com>
Date: Thu, 2 Jun 2022 21:15:31 +0000
Subject: [PATCH] README

---
 examples/chef/README.md | 45 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 45 insertions(+)

diff --git a/examples/chef/README.md b/examples/chef/README.md
index 0ccd51193bae73..43b1e744608f84 100644
--- a/examples/chef/README.md
+++ b/examples/chef/README.md
@@ -58,3 +58,48 @@ Run `chef.py -h` to see the available commands
 3. Click on `Save As` and save the file with the name of your new device type
    into the `devices` folder. This device is now available for the script. See
    `chef.py -h` for a list of devices available.
+
+## CI
+
+### zzz_generated
+
+To eliminate a dependnecy on ZAP in CI jobs, all chef examples found in `examples/chef/devices` must have their output from the ZAP tool cached in `examples/chef/zzz_generated`.
+
+To generate the cache, one may execute chef with the option `--generate_zzz`. This will run ZAP for all devices in `examples/chef/devices` and place the output into the appropriate directory structure.
+
+Other than the output from the ZAP tool, the cache directory contains two additional files for each device:
+- `INPUTMD5.txt` contains the md5 hex digest of the ZAP file used to generate the directory.
+- `ZAPSHA.txt` contains the commit of ZAP in the user's tree when the directory was generated.
+
+```
+zzz_generated/
+└── lighting-app
+    ├── INPUTMD5.txt
+    ├── zap-generated
+    │   ├── access.h
+    │   ├── af-gen-event.h
+    │   └── ...
+    └── ZAPSHA.txt
+```
+
+These additional files will be used by the CI jobs to validate whether the cache must be regenerated i.e. regeneration is needed when ZAP or the input ZAP files change.
+
+### Workflow
+
+All CI jobs for chef can be found in `.github/workflows/chef.yaml`.
+
+#### Validate
+
+The workflow begins by calling chef with `--validate_zzz`.
+
+`--validate_zzz` will recalculate the current ZAP commit and the md5 of all example ZAP files and compare with what is committed to `zzz_generated`.
+
+If the validation job fails, it will provide instructions to repair `zzz_generated` and no builds will run.
+
+#### Build
+
+Once the validation job is complete, there is a separate job for each platform, which run in parallel.
+
+These jobs use a platform-specific image with base `chip-build`.
+
+The build jobs call chef with the options `--ci -t <PLATFORM>`. The `--ci` flag will build all examples for the specified platform and for all devices specified in `_CI_ALLOW_LIST` defined in `chef.py` (so long as these devices are also in `/devices`).