From 5256d4ccd84d6ab6b4e61bcc0317ccdaa490b916 Mon Sep 17 00:00:00 2001
From: Tai Groot <tai@taigrr.com>
Date: Wed, 10 Jun 2026 08:31:37 +0000
Subject: [PATCH] fix(read): return errors for uninitialized devices

---
 temper_linux_test.go | 26 ++++++++++++++++++++++++++
 temperctx_linux.go   |  7 +++++++
 2 files changed, 33 insertions(+)

diff --git a/temper_linux_test.go b/temper_linux_test.go
index a96c63a..439789a 100644
--- a/temper_linux_test.go
+++ b/temper_linux_test.go
@@ -65,6 +65,32 @@ func TestCloseSafeOnNilAndZeroValue(t *testing.T) {
 	}
 }
 
+func TestReadCSafeOnNilAndZeroValue(t *testing.T) {
+	var nilTemper *Temper
+	if _, err := nilTemper.ReadC(); err != errUninitializedTemper {
+		t.Fatalf("ReadC() on nil Temper error = %v, want %v", err, errUninitializedTemper)
+	}
+
+	var zero Temper
+	if _, err := zero.ReadC(); err != errUninitializedTemper {
+		t.Fatalf("ReadC() on zero-value Temper error = %v, want %v", err, errUninitializedTemper)
+	}
+}
+
+func TestReadFWithContextSafeOnNilAndZeroValue(t *testing.T) {
+	ctx := context.Background()
+
+	var nilTemper *Temper
+	if _, err := nilTemper.ReadFWithContext(ctx); err != errUninitializedTemper {
+		t.Fatalf("ReadFWithContext() on nil Temper error = %v, want %v", err, errUninitializedTemper)
+	}
+
+	var zero Temper
+	if _, err := zero.ReadFWithContext(ctx); err != errUninitializedTemper {
+		t.Fatalf("ReadFWithContext() on zero-value Temper error = %v, want %v", err, errUninitializedTemper)
+	}
+}
+
 func TestIsInputDevice(t *testing.T) {
 	if isInputDevice("temper999") {
 		t.Error("expected false for non-existent hidraw device")
diff --git a/temperctx_linux.go b/temperctx_linux.go
index 959a505..46c8d4b 100644
--- a/temperctx_linux.go
+++ b/temperctx_linux.go
@@ -3,13 +3,20 @@ package temper
 import (
 	"context"
 	"encoding/hex"
+	"errors"
 	"fmt"
 	"strconv"
 )
 
+var errUninitializedTemper = errors.New("temper device is uninitialized")
+
 // ReadCWithContext reads the internal sensor temperature in Celsius,
 // respecting the provided context for cancellation/timeout.
 func (t *Temper) ReadCWithContext(ctx context.Context) (float32, error) {
+	if t == nil || t.reader == nil || t.writer == nil {
+		return 0, errUninitializedTemper
+	}
+
 	t.lock.Lock()
 	defer t.lock.Unlock()