From 227bad9e997ac890338bc23fc4a9a7e906c5d6e7 Mon Sep 17 00:00:00 2001
From: Alexis Svinartchouk <alexis@resin.io>
Date: Fri, 31 Jan 2020 16:23:50 +0100
Subject: [PATCH] Keep leds sysfs files open

Change-type: patch
---
 lib/gui/app/models/leds.ts | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/lib/gui/app/models/leds.ts b/lib/gui/app/models/leds.ts
index 7ad1159d..d018abdb 100644
--- a/lib/gui/app/models/leds.ts
+++ b/lib/gui/app/models/leds.ts
@@ -21,17 +21,26 @@ import * as settings from './settings';
 import { observe } from './store';
 
 class Led {
+	private handle: fs.FileHandle;
 	private lastValue?: number;
 
 	constructor(private path: string) {}
 
+	private async open() {
+		if (this.handle === undefined) {
+			this.handle = await fs.open(this.path, 'w');
+		}
+	}
+
 	public async setIntensity(intensity: number) {
 		if (intensity < 0 || intensity > 1) {
 			throw new Error('Led intensity must be between 0 and 1');
 		}
 		const value = Math.round(intensity * 255);
 		if (value !== this.lastValue) {
-			await fs.writeFile(this.path, value.toString());
+			await this.open();
+			await this.handle.write(value.toString(), 0);
+			// On a regular file we would also need to truncate to the written value length but it looks like it's not the case on sysfs files
 			this.lastValue = value;
 		}
 	}