From 38b4e0abdcae7e6da666e09759bbedd69e8c24bc Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=B8ren=20Rasmussen?= <sr@jondahl.net>
Date: Sat, 15 Jun 2024 22:02:15 +0200
Subject: [PATCH] Add w1-therm gokrazy module

---
 cmd/w1-therm/README.md |  3 ++
 cmd/w1-therm/main.go   | 91 ++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 94 insertions(+)
 create mode 100644 cmd/w1-therm/README.md
 create mode 100644 cmd/w1-therm/main.go

diff --git a/cmd/w1-therm/README.md b/cmd/w1-therm/README.md
new file mode 100644
index 0000000..d9084b5
--- /dev/null
+++ b/cmd/w1-therm/README.md
@@ -0,0 +1,3 @@
+This package provides support for using 1-wire DS18B20 with gokrazy!
+
+The package just loads the kernel module.
diff --git a/cmd/w1-therm/main.go b/cmd/w1-therm/main.go
new file mode 100644
index 0000000..295a4a7
--- /dev/null
+++ b/cmd/w1-therm/main.go
@@ -0,0 +1,91 @@
+// w1-therm is a gokrazy helper that loads 1-wire kernel modules on boot.
+//
+// Example:
+//
+//	Include the w1-therm package in your gokr-packer command:
+//	% gokr-packer -update=yes \
+//	  github.com/gokrazy/breakglass \
+//	  git.joco.dk/snr/fermentord/cmd/w1-therm
+package main
+
+import (
+	"bytes"
+	"flag"
+	"fmt"
+	"log"
+	"os"
+	"path/filepath"
+	"strings"
+
+	"golang.org/x/sys/unix"
+)
+
+func logic() error {
+	flag.Parse()
+
+	for _, mod := range []string{
+		"kernel/drivers/w1/wire.ko",
+		"kernel/drivers/w1/masters/w1-gpio.ko",
+		"kernel/drivers/w1/slaves/w1-therm.ko",
+	} {
+		if err := loadModule(mod); err != nil && !os.IsNotExist(err) {
+			return err
+		}
+	}
+
+	dev := "w1_bus_master1"
+	target, err := checkOneWireInterface(dev)
+	if err != nil {
+		log.Printf("Bluetooth interface %v not found.", target)
+	} else {
+		fmt.Printf("Bluetooth device %v: %v\n", dev, target)
+	}
+
+	// gokrazy should not supervise this process even when manually started.
+	os.Exit(125)
+	return nil
+}
+
+func checkOneWireInterface(device string) (string, error) {
+	name := fmt.Sprintf("/sys/bus/w1/devices/%v", device)
+	target, err := os.Readlink(name)
+	if err != nil {
+		return "", fmt.Errorf("OneWire bus master %v not found", device)
+	}
+	return target, nil
+}
+
+func loadModule(mod string) error {
+	f, err := os.Open(filepath.Join("/lib/modules", release, mod))
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+
+	if err := unix.FinitModule(int(f.Fd()), "", 0); err != nil {
+		if err != unix.EEXIST &&
+			err != unix.EBUSY &&
+			err != unix.ENODEV &&
+			err != unix.ENOENT {
+			return fmt.Errorf("FinitModule(%v): %v", mod, err)
+		}
+	}
+	modname := strings.TrimSuffix(filepath.Base(mod), ".ko")
+	log.Printf("modprobe %v", modname)
+	return nil
+}
+
+var release = func() string {
+	var uts unix.Utsname
+	if err := unix.Uname(&uts); err != nil {
+		fmt.Fprintf(os.Stderr, "minitrd: %v\n", err)
+		os.Exit(1)
+	}
+	return string(uts.Release[:bytes.IndexByte(uts.Release[:], 0)])
+}()
+
+func main() {
+	if err := logic(); err != nil {
+		log.Fatal(err)
+	}
+}