Add PowerFanConfig config backend

This config backend uses ConfigJsonConfigBackend to write to
managed fields in the "os" key, in order to set power and fan
configs. In config.json, the expected managed schema is:
```
{
  os: {
    power: {
      mode: string
    },
    fan: {
      profile: string
    }
  }
}
```

There may be other keys in os which are not managed by the Supervisor,
so the Supervisor should not read or write to them.

After the Supervisor writes to config.json, host services os-power-mode
and os-fan-profile pick up the changes, on reboot in the former's case
and at runtime in the latter's case. The changes are applied by the host
services, which the Supervisor does not manage aside from streaming
their service logs to the dashboard (see next commit).

Change-type: minor
Signed-off-by: Christina Ying Wang <[email protected]>

src/config/backends/config-txt.ts

@@ -2,6 +2,7 @@ import _ from 'lodash';
 
 import type { ConfigOptions } from './backend';
 import { ConfigBackend } from './backend';
+import { PowerFanConfig } from './power-fan';
 import * as constants from '../../lib/constants';
 import log from '../../lib/supervisor-console';
 import { exists } from '../../lib/fs-utils';
@@ -231,11 +232,21 @@ export class ConfigTxt extends ConfigBackend {
 	}
 
 	public isSupportedConfig(configName: string): boolean {
-		return !ConfigTxt.forbiddenConfigKeys.includes(configName);
+		return (
+			!ConfigTxt.forbiddenConfigKeys.includes(configName) &&
+			// power_mode and fan_profile are managed by the power-fan backend, so
+			// need to be excluded here as the config var name prefix is the same.
+			!PowerFanConfig.isSupportedConfig(configName)
+		);
 	}
 
 	public isBootConfigVar(envVar: string): boolean {
-		return envVar.startsWith(ConfigTxt.bootConfigVarPrefix);
+		return (
+			envVar.startsWith(ConfigTxt.bootConfigVarPrefix) &&
+			// power_mode and fan_profile are managed by the power-fan backend, so
+			// need to be excluded here as the config var name prefix is the same.
+			!PowerFanConfig.isSupportedConfig(envVar)
+		);
 	}
 
 	public processConfigVarName(envVar: string): string {

src/config/backends/index.ts

@@ -4,6 +4,8 @@ import { ConfigTxt } from './config-txt';
 import { ConfigFs } from './config-fs';
 import { Odmdata } from './odmdata';
 import { SplashImage } from './splash-image';
+import { PowerFanConfig } from './power-fan';
+import { configJsonBackend } from '..';
 
 export const allBackends = [
 	new Extlinux(),
@@ -12,6 +14,7 @@ export const allBackends = [
 	new ConfigFs(),
 	new Odmdata(),
 	new SplashImage(),
+	new PowerFanConfig(configJsonBackend),
 ];
 
 export function matchesAnyBootConfig(envVar: string): boolean {

src/config/backends/power-fan.ts

@@ -0,0 +1,160 @@
+import { isRight } from 'fp-ts/lib/Either';
+import Reporter from 'io-ts-reporters';
+
+import { ConfigBackend } from './backend';
+import type { ConfigOptions } from './backend';
+import { schemaTypes } from '../schema-type';
+import log from '../../lib/supervisor-console';
+import * as constants from '../../lib/constants';
+import type ConfigJsonConfigBackend from '../configJson';
+
+const isNullOrUndefined = (v: unknown): v is null | undefined =>
+	v === null || v === undefined;
+
+/**
+ * A backend to handle Jetson power and fan control
+ *
+ * Supports:
+ * 	- {BALENA|RESIN}_HOST_CONFIG_power_mode = "low" | "mid" | "high" | "$MODE_ID"
+ * 	- {BALENA|RESIN}_HOST_CONFIG_fan_profile = "quiet" | "default" | "cool" | "$MODE_ID"
+ */
+export class PowerFanConfig extends ConfigBackend {
+	private static readonly PREFIX = `${constants.hostConfigVarPrefix}CONFIG_`;
+	private static readonly CONFIGS = new Set(['power_mode', 'fan_profile']);
+
+	private readonly configJson: ConfigJsonConfigBackend;
+	public constructor(configJson: ConfigJsonConfigBackend) {
+		super();
+		this.configJson = configJson;
+	}
+
+	private static stripPrefix(name: string): string {
+		if (!name.startsWith(PowerFanConfig.PREFIX)) {
+			return name;
+		}
+		return name.substring(PowerFanConfig.PREFIX.length);
+	}
+
+	public async matches(deviceType: string): Promise<boolean> {
+		// We only support Jetpack 6 devices for now, which includes all Orin devices
+		// except for jetson-orin-nx-xv3 which is still on Jetpack 5 as of OS v5.1.36
+		return new Set([
+			'jetson-agx-orin-devkit',
+			'jetson-agx-orin-devkit-64gb',
+			'jetson-orin-nano-devkit-nvme',
+			'jetson-orin-nano-seeed-j3010',
+			'jetson-orin-nx-seeed-j4012',
+			'jetson-orin-nx-xavier-nx-devkit',
+		]).has(deviceType);
+	}
+
+	public async getBootConfig(): Promise<ConfigOptions> {
+		// Get relevant config.json contents
+		let rawConf: unknown;
+		try {
+			rawConf = await this.configJson.get('os');
+		} catch (e: unknown) {
+			log.error(
+				`Failed to read config.json while getting power / fan configs: ${(e as Error).message ?? e}`,
+			);
+			return {};
+		}
+
+		// Decode to known schema from unknown type
+		const powerFanConfig = schemaTypes.os.type.decode(rawConf);
+
+		if (isRight(powerFanConfig)) {
+			const conf = powerFanConfig.right;
+			return {
+				...(!isNullOrUndefined(conf.power?.mode) && {
+					power_mode: conf.power.mode,
+				}),
+				...(!isNullOrUndefined(conf.fan?.profile) && {
+					fan_profile: conf.fan.profile,
+				}),
+			};
+		} else {
+			return {};
+		}
+	}
+
+	public async setBootConfig(opts: ConfigOptions): Promise<void> {
+		// Read power & fan boot configs from config.json
+		let rawConf: unknown;
+		try {
+			rawConf = await this.configJson.get('os');
+		} catch (err: unknown) {
+			log.error(`${(err as Error).message ?? err}`);
+			return;
+		}
+
+		// Decode from unknown to known schema
+		const decodedCurrentConf = schemaTypes.os.type.decode(rawConf);
+		if (!isRight(decodedCurrentConf)) {
+			log.error(
+				'Failed to decode current power & fan config:',
+				Reporter.report(decodedCurrentConf),
+			);
+			return;
+		}
+		const currentConf = decodedCurrentConf.right;
+
+		// Filter out unsupported options
+		const supportedOpts = Object.fromEntries(
+			Object.entries(opts).filter(([key]) => this.isSupportedConfig(key)),
+		) as { power_mode?: string; fan_profile?: string };
+
+		const targetConf = structuredClone(currentConf);
+
+		// Iterate over supported configs Set and update targetConf
+		// Cast key to only members of PowerFanConfig.CONFIGS to avoid TypeScript errors
+		// const key should be of type 'power_mode' or 'fan_profile' ONLY
+
+		// Update or delete power mode
+		if ('power_mode' in supportedOpts) {
+			targetConf.power = {
+				...targetConf.power,
+				mode: supportedOpts.power_mode,
+			};
+		} else {
+			delete targetConf.power;
+		}
+
+		// Update or delete fan profile
+		if ('fan_profile' in supportedOpts) {
+			targetConf.fan = {
+				...targetConf.fan,
+				profile: supportedOpts.fan_profile,
+			};
+		} else {
+			delete targetConf.fan;
+		}
+
+		await this.configJson.set({ os: targetConf });
+	}
+
+	public isSupportedConfig(name: string): boolean {
+		return PowerFanConfig.CONFIGS.has(PowerFanConfig.stripPrefix(name));
+	}
+
+	// A static version of isSupportedConfig for other backends to use to exclude power & fan configs
+	public static isSupportedConfig(name: string): boolean {
+		return PowerFanConfig.CONFIGS.has(PowerFanConfig.stripPrefix(name));
+	}
+
+	public isBootConfigVar(envVar: string): boolean {
+		return PowerFanConfig.CONFIGS.has(PowerFanConfig.stripPrefix(envVar));
+	}
+
+	public processConfigVarName(envVar: string): string {
+		return PowerFanConfig.stripPrefix(envVar).toLowerCase();
+	}
+
+	public processConfigVarValue(_key: string, value: string): string {
+		return value;
+	}
+
+	public createConfigVarName(name: string): string | null {
+		return `${PowerFanConfig.PREFIX}${name}`;
+	}
+}