Fix processing of dtoverlay/dtparams on config.txt

DT overlays and DT params need to be consumed in the order that they
appear on the file. DT params apply to the last dtoverlay defined on the
file, or to the base overlay.

This commit updates config.txt parsing to consider this ordering, and it
also ensures global dtparams are written first so they cannot be
overriden by later overlays.

Because of the more strict parsing method, it is possible that existing
HOST_CONFIG vars do not match the interpretation of the parser. If
that's the case, the supervisor will re-apply the target state which
will cause the device to reboot.

Change-type: major

src/config/backends/config-txt.ts

@@ -26,6 +26,11 @@ function isArrayConfig(x: string): x is ArrayConfig {
 	return x != null && ARRAY_CONFIGS.includes(x as any);
 }
 
+// The DTOverlays type is a collection of DtParams
+type DTParam = string;
+type DTOverlays = { [name: string]: DTParam[] };
+const BASE_OVERLAY = '';
+
 /**
  * A backend to handle Raspberry Pi host configuration
  *
@@ -87,6 +92,9 @@ export class ConfigTxt extends ConfigBackend {
 		const conf: ConfigTxtOptions = {};
 		const configStatements = configContents.split(/\r?\n/);
 
+		let currOverlay = BASE_OVERLAY;
+		const dtOverlays: DTOverlays = { [BASE_OVERLAY]: [] };
+
 		for (const configStr of configStatements) {
 			// Don't show warnings for comments and empty lines
 			const trimmed = configStr.trimStart();
@@ -103,10 +111,27 @@ export class ConfigTxt extends ConfigBackend {
 					// configuration
 					conf[key] = value;
 				} else {
-					// TODO: dtparams and dtoverlays need to be treated as a special case
-					// Otherwise push the new value to the array
-					const arrayConf = conf[key] == null ? [] : conf[key]!;
-					arrayConf.push(value);
+					// dtparams and dtoverlays need to be treated as a special case
+					if (key === 'dtparam') {
+						dtOverlays[currOverlay].push(value);
+					} else if (key === 'dtoverlay') {
+						// Assume that the first element is the overlay name
+						// we don't validate that the value is well formed
+						const [overlay, ...params] = value.split(',');
+
+						// Update the DTO for next dtparam
+						currOverlay = overlay;
+						if (dtOverlays[overlay] == null) {
+							dtOverlays[overlay] = [];
+						}
+
+						// Add params to the list
+						dtOverlays[overlay].push(...params);
+					} else {
+						// Otherwise push the new value to the array
+						const arrayConf = conf[key] == null ? [] : conf[key]!;
+						arrayConf.push(value);
+					}
 				}
 				continue;
 			}
@@ -122,20 +147,48 @@ export class ConfigTxt extends ConfigBackend {
 			}
 		}
 
+		// Convert the base overlay to global dtparams
+		const baseOverlay = dtOverlays[BASE_OVERLAY];
+		delete dtOverlays[BASE_OVERLAY];
+		if (baseOverlay.length > 0) {
+			conf.dtparam = baseOverlay;
+		}
+
+		// Convert dtoverlays to array format
+		const overlayEntries = Object.entries(dtOverlays);
+		if (overlayEntries.length > 0) {
+			conf.dtoverlay = overlayEntries.map(([overlay, params]) =>
+				[overlay, ...params].join(','),
+			);
+		}
+
 		return conf;
 	}
 
-	public async setBootConfig(opts: ConfigOptions): Promise<void> {
-		const confStatements = Object.entries(opts).flatMap(([key, value]) => {
-			if (key === 'initramfs') {
-				return `${key} ${value}`;
-			} else if (Array.isArray(value)) {
-				return value.map((entry) => `${key}=${entry}`);
-			} else {
-				return `${key}=${value}`;
+	public async setBootConfig(opts: ConfigTxtOptions): Promise<void> {
+		const confStatements = Object.entries(opts)
+			// Treat dtoverlays separately
+			.filter(([key]) => key !== 'dtoverlay')
+			.flatMap(([key, value]) => {
+				if (key === 'initramfs') {
+					return `${key} ${value}`;
+				} else if (Array.isArray(value)) {
+					return value.map((entry) => `${key}=${entry}`);
+				} else {
+					return `${key}=${value}`;
+				}
+			});
+
+		// Split dtoverlays from their params to avoid running into char limits
+		// and write at the end to prevent overriding the base overlay
+		if (opts.dtoverlay != null) {
+			for (const entry of opts.dtoverlay) {
+				const [overlay, ...params] = entry.split(',');
+				confStatements.push(`dtoverlay=${overlay}`);
+				confStatements.push(...params.map((p) => `dtparam=${p}`));
 			}
-		});
-		// TODO: split dtoverlay into dtparams
+		}
+
 		const confStr = `${confStatements.join('\n')}\n`;
 		await hostUtils.writeToBoot(ConfigTxt.bootConfigPath, confStr);
 	}