[Telemetry] Add docs on how set the OEM name

This CL adds documentation on how to set the OEM name that
is used by the Telemetry extension and the cros_healthd
daemon. This documentation is generic and does not mention
custom fields for a certain OEM.

Bug: b/255740685
Change-Id: I01be1aff3ec5e4c7aa6cddc369580b1f8cbe6c1a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4008224
Commit-Queue: Bastian Kersting <bkersting@google.com>
Reviewed-by: Oleh Lamzin <lamzin@google.com>
Cr-Commit-Position: refs/heads/main@{#1069034}

docs/telemetry_extension/add_oem_name.md

@@ -0,0 +1,149 @@
+# Customization Guide - OEM Name
+
+# Objective
+Provide the instructions on the OEM name customization on ChromeOS devices.
+
+[TOC]
+
+# Overview
+We have proposed a hybrid approach "cros_config first, fallback to VPD" for OEM
+name customization. This approach first tries to search for the OEM name in
+cros_config and checks a VPD field if the name is not present. Right now
+(October, 2022) only the cros_config part is implemented; the VPD part is in
+progress. In general the OEM name field is used to differentiate between
+different OEMs on a ChromeOS device. The field is currently used by the
+[Telemetry Extension](README.md) and is a requirement to use the Extension.
+This guide explains how to set the OEM name in cros_config.
+
+## Rollout schedule
+Please note that the changes made here follow the Chrome Release Cycle (actual
+timeline can be found in
+[Chromium Dashboard](https://chromiumdash.appspot.com/schedule)), which means
+it will take at least 6 weeks to rollout your changes to the public.
+
+# Instructions
+This section provides the instructions on how to check OEM name config, and set
+/verify the OEM name for models with or without Boxster.
+
+> **_NOTE:_** It is your responsibility to make sure the OEM name you fill in is
+correct. Neither cros-config nor Boxster validate that value.
+
+## Check & Set OEM name
+### Models with Boxster
+
+1. In `config.star`
+    1. Find a variable initialized with `device_brand.create` (See
+       [Troubleshooting](#Troubleshooting) if you cannot find it). Usually named  `_DEVICE_BRAND`.
+    2. Find the variable (`_FAKE_OEM` in our example) that is passed to `oem_id`
+       and make sure the value inside it is correct. In case you need to modify
+       the existing OEM name, you could follow the sample CL
+       [crrev.com/c/3627425](http://crrev.com/c/3627425).
+    3. Add a keyword argument `export_oem_info = True`.
+2. Reflect your changes in `generated/config.jsonproto` and
+`sw_build_config/platform/chromeos-config/generated/project-config.json` by
+running: `./config/bin/gen_config config.star`.
+3. Commit your changes. Sample CL:
+[crrev.com/c/3385463](http://crrev.com/c/3385463).
+
+The configuration in  `config.star` would look like this:
+```python
+// config.star
+_FAKE_OEM = partner.create("FAKE_OEM") # Make sure it’s correct
+...
+_DEVICE_BRAND = device_brand.create(
+brand_name = "Fake ChromeOS Device Brandname",
+design_id = _DESIGN_ID,
+oem_id = _FAKE_OEM.id, # This argument is required
+brand_code = "AAAA",
+export_oem_info = True, # Add this line
+)
+```
+
+### Models without Boxster
+
+1. in `model.yaml`
+    1. Make sure inside `base-config` there’s another dictionary named `branding`
+       containing an entry with key `oem-name` and value `{{$oem-name}}`.
+       Optionally, you can add another entry `$oem-name` with value `""` (an
+       empty string) which will be used as default value.
+    2. Add a new entry `$oem-name` whose value is the OEM name you would like to
+       set in `chromeos.devices[].products[]`.
+    3. Commit your changes and upload them to the internal Gerrit.
+
+An example `model.yaml` could look somewhat like this:
+```yaml
+base-config: &base_config
+ ...
+ branding:
+   $oem-name: ""
+   oem-name: "{{$oem-name}}"
+ ...
+ devices:
+   ...
+   - $device-name: "foo"
+     $has-smart-battery-info: true
+     products:
+       - $brand-code: "FOO"
+         $marketing-name: "TBD"
+         $oem-name: "OEM_A" # This is what you set.
+     skus:
+       - $sku-id-val: 42
+         config: *foo_config
+```
+
+## Verify the OEM name
+
+You can verify the OEM name configuration by running the following command:
+```
+cros-health-tool telem --category=system
+```
+
+Check if `os_info.oem_name` is present and correct.
+A sample output would look somewhat like that:
+```
+$ cros-health-tool telem --category=system
+{
+  "dmi_info": {
+     ...
+  },
+  "os_info": {
+     "boot_mode": "cros_secure",
+     "code_name": "foo",
+     "marketing_name": "TBD",
+     "oem_name": "OEM_A",    # check this line
+     ...
+  },
+  "vpd_info": {
+     ...
+  }
+```
+
+## Troubleshooting
+
+### No device_brand.create in config.star?
+In some projects, you might see `_DEVICE_BRAND` is initialized with
+`program.brand`. In this case, you need to:
+
+1. Go to `program/program.star` (note that this file is in a different repo
+`chromeos/program/${BOARD}` as `program/` is a soft link) and modify the
+`_brand` function:
+2. Go back to `config.star` and add the parameter `export_oem_info = True` to
+the `program.brand` function.
+3. Regenerate config.
+
+Sample `program/program.star`:
+```python
+def _brand(design_id, oem_id = None, brand_code = _DEFAULT_BRAND_CODE, brand_name = None, export_oem_info = False):
+   return device_brand.create(
+       brand_name = brand_name,
+       design_id = design_id,
+       oem_id = oem_id,
+       brand_code = brand_code,
+       export_oem_info = export_oem_info,
+   )
+```
+
+Sample `config.star`:
+```python
+_DEVICE_BRAND = program.brand(_FOO_DESIGN_ID, ..., export_oem_info = True)
+```