fix: improve HAL error messages in battery_health and softap_wifi_hal examples

Add contextual hints when HAL calls fail: the health HAL may not be
available on the device or may have died, and WiFi HAL access may be
restricted by SELinux. This helps users diagnose why examples fail on
devices where HAL services are dead or inaccessible.

Author: xaionaro@dx.center

examples/battery_health/main.go

@@ -38,22 +38,23 @@ func main() {
 
 	svc, err := sm.GetService(ctx, servicemanager.ServiceName("android.hardware.health.IHealth/default"))
 	if err != nil {
-		fmt.Fprintf(os.Stderr, "get health HAL: %v (may be blocked by SELinux)\n", err)
+		fmt.Fprintf(os.Stderr, "get health HAL: %v\n", err)
+		fmt.Fprintf(os.Stderr, "(health HAL may not be available on this device, or access may be blocked by SELinux)\n")
 		os.Exit(1)
 	}
 
 	h := health.NewHealthProxy(svc)
 
 	capacity, err := h.GetCapacity(ctx)
 	if err != nil {
-		fmt.Fprintf(os.Stderr, "GetCapacity: %v\n", err)
+		fmt.Fprintf(os.Stderr, "GetCapacity: %v (health HAL may have died or returned an error)\n", err)
 	} else {
 		fmt.Printf("Battery level:    %d%%\n", capacity)
 	}
 
 	status, err := h.GetChargeStatus(ctx)
 	if err != nil {
-		fmt.Fprintf(os.Stderr, "GetChargeStatus: %v\n", err)
+		fmt.Fprintf(os.Stderr, "GetChargeStatus: %v (health HAL may have died or returned an error)\n", err)
 	} else {
 		statusName := "unknown"
 		switch status {
@@ -73,14 +74,14 @@ func main() {
 
 	current, err := h.GetCurrentNowMicroamps(ctx)
 	if err != nil {
-		fmt.Fprintf(os.Stderr, "GetCurrentNowMicroamps: %v\n", err)
+		fmt.Fprintf(os.Stderr, "GetCurrentNowMicroamps: %v (health HAL may have died or returned an error)\n", err)
 	} else {
 		fmt.Printf("Current draw:     %d µA\n", current)
 	}
 
 	counter, err := h.GetChargeCounterUah(ctx)
 	if err != nil {
-		fmt.Fprintf(os.Stderr, "GetChargeCounterUah: %v\n", err)
+		fmt.Fprintf(os.Stderr, "GetChargeCounterUah: %v (health HAL may have died or returned an error)\n", err)
 	} else {
 		fmt.Printf("Charge counter:   %d µAh\n", counter)
 	}

examples/softap_wifi_hal/main.go

@@ -62,14 +62,15 @@ func main() {
 	started, err := wifiHal.IsStarted(ctx)
 	if err != nil {
 		fmt.Fprintf(os.Stderr, "IsStarted: %v\n", err)
+		fmt.Fprintf(os.Stderr, "(WiFi HAL may have died or access may be restricted by SELinux)\n")
 	} else {
 		fmt.Printf("WiFi HAL started: %v\n", started)
 	}
 
 	// List available WiFi chips.
 	chipIds, err := wifiHal.GetChipIds(ctx)
 	if err != nil {
-		fmt.Fprintf(os.Stderr, "GetChipIds: %v\n", err)
+		fmt.Fprintf(os.Stderr, "GetChipIds: %v (WiFi HAL may have died or access may be restricted by SELinux)\n", err)
 		return
 	}