Temp: fix severial issues. Fixes #398

1. Temp detection has been gated behind of `--*-temp`. Don't make it a slow operation
2. According to [the kernel doc](https://www.kernel.org/doc/Documentation/hwmon/sysfs-interface), `temp1_input` is millidegree Celsius, which should be divided by 1000
3. There is no `/sys/class/hwmon/hwmon3/device/class` on my laptop, but `/sys/class/hwmon/hwmon3/device/device/class`. Need to confirm with @LinusDierheimer
4. Small code optimizations

src/detection/cpu/cpu_linux.c

@@ -67,9 +67,9 @@ static double getFrequency(const char* info, const char* scaling)
     return getGHz(scaling);
 }
 
-static double detectCPUTemp(const FFinstance* instance)
+static double detectCPUTemp()
 {
-    const FFTempsResult* temps = ffDetectTemps(instance);
+    const FFTempsResult* temps = ffDetectTemps();
 
     for(uint32_t i = 0; i < temps->values.length; i++)
     {

src/detection/gpu/gpu_linux.c

@@ -146,20 +146,16 @@ static void pciDetectDriverName(FFGPUResult* gpu, PCIData* pci, struct pci_dev*
     ffStrbufDestroy(&path);
 }
 
-static void pciDetectTemperatur(const FFinstance* instance, FFGPUResult* gpu, struct pci_dev* device)
+static void pciDetectTemperatur(FFGPUResult* gpu, struct pci_dev* device)
 {
-    const FFTempsResult* tempsResult = ffDetectTemps(instance);
+    const FFTempsResult* tempsResult = ffDetectTemps();
 
     for(uint32_t i = 0; i < tempsResult->values.length; i++)
     {
         FFTempValue* tempValue = ffListGet(&tempsResult->values, i);
 
-        uint32_t tempClass;
-        if(sscanf(tempValue->deviceClass.chars, "%x", &tempClass) != 1)
-            continue;
-
         //The kernel exposes the device class multiplied by 256 for some reason
-        if(tempClass == device->device_class * 256)
+        if(tempValue->deviceClass == device->device_class * 256)
         {
             gpu->temperature = tempValue->value;
             return;
@@ -233,7 +229,7 @@ static void pciHandleDevice(const FFinstance* instance, FFlist* results, PCIData
 
     gpu->temperature = FF_GPU_TEMP_UNSET;
     if(instance->config.gpuTemp)
-        pciDetectTemperatur(instance, gpu, device);
+        pciDetectTemperatur(gpu, device);
 }
 
 static const char* pciDetectGPUs(const FFinstance* instance, FFlist* gpus)

src/detection/temps/temps_linux.c

@@ -8,18 +8,19 @@
 
 static bool parseHwmonDir(FFstrbuf* dir, FFTempValue* value)
 {
+    //https://www.kernel.org/doc/Documentation/hwmon/sysfs-interface
     uint32_t dirLength = dir->length;
 
-    FFstrbuf valueBuffer;
+    FF_STRBUF_AUTO_DESTROY valueBuffer;
     ffStrbufInit(&valueBuffer);
 
     ffStrbufAppendS(dir, "temp1_input");
-    ffReadFileBuffer(dir->chars, &valueBuffer);
+    if(!ffReadFileBuffer(dir->chars, &valueBuffer))
+        return false;
+
     ffStrbufSubstrBefore(dir, dirLength);
 
-    value->value = ffStrbufToDouble(&valueBuffer);
-
-    ffStrbufDestroy(&valueBuffer);
+    value->value = ffStrbufToDouble(&valueBuffer) / 1000; // valueBuffer is millidegree Celsius
 
     if(value->value != value->value)
         return false;
@@ -28,14 +29,16 @@ static bool parseHwmonDir(FFstrbuf* dir, FFTempValue* value)
     ffReadFileBuffer(dir->chars, &value->name);
     ffStrbufSubstrBefore(dir, dirLength);
 
-    ffStrbufAppendS(dir, "device/class");
-    ffReadFileBuffer(dir->chars, &value->deviceClass);
+    ffStrbufAppendS(dir, "device/device/class");
+
+    if(ffReadFileBuffer(dir->chars, &valueBuffer))
+        value->deviceClass = (uint32_t) strtoul(valueBuffer.chars, NULL, 16);
     ffStrbufSubstrBefore(dir, dirLength);
 
-    return value->name.length > 0 || value->deviceClass.length > 0;
+    return value->name.length > 0 || value->deviceClass > 0;
 }
 
-const FFTempsResult* ffDetectTemps(const FFinstance* instance)
+const FFTempsResult* ffDetectTemps()
 {
     static FFTempsResult result;
     static FFThreadMutex mutex = FF_THREAD_MUTEX_INITIALIZER;
@@ -49,13 +52,6 @@ const FFTempsResult* ffDetectTemps(const FFinstance* instance)
     }
     init = true;
 
-    if(!instance->config.allowSlowOperations)
-    {
-        ffListInitA(&result.values, sizeof(FFTempValue), 0);
-        ffThreadMutexUnlock(&mutex);
-        return &result;
-    }
-
     ffListInitA(&result.values, sizeof(FFTempValue), 16);
 
     FFstrbuf baseDir;
@@ -83,11 +79,10 @@ const FFTempsResult* ffDetectTemps(const FFinstance* instance)
 
         FFTempValue* temp = ffListAdd(&result.values);
         ffStrbufInit(&temp->name);
-        ffStrbufInit(&temp->deviceClass);
+        temp->deviceClass = 0;
         if(!parseHwmonDir(&baseDir, temp))
         {
             ffStrbufDestroy(&temp->name);
-            ffStrbufDestroy(&temp->deviceClass);
             --result.values.length;
         }
 

src/detection/temps/temps_linux.h

@@ -8,7 +8,7 @@
 typedef struct FFTempValue
 {
     FFstrbuf name;
-    FFstrbuf deviceClass;
+    uint32_t deviceClass;
     double value;
 } FFTempValue;
 
@@ -17,6 +17,6 @@ typedef struct FFTempsResult
     FFlist values; //List of FFTempValue
 } FFTempsResult;
 
-const FFTempsResult* ffDetectTemps(const FFinstance* instance);
+const FFTempsResult* ffDetectTemps();
 
 #endif