gpu_fdinfo: add sensor fallback for non-PCI GPU

Some GPUs do not use PCI as bus (e.g. MSM devices). When current GPU do
not have a pci_dev, search global `/sys/class/hwmon` directory for a
`gpu` sensor.

Signed-off-by: Ettore Chimenti <[email protected]>

src/gpu_fdinfo.cpp

@@ -129,14 +129,38 @@ float GPU_fdinfo::get_memory_used()
 void GPU_fdinfo::find_hwmon()
 {
     std::string device = "/sys/bus/pci/devices/" + pci_dev + "/hwmon";
+    std::string hwmon;
 
     if (!fs::exists(device)) {
         SPDLOG_DEBUG("hwmon: hwmon directory {} doesn't exist.", device);
-        return;
-    }
+        SPDLOG_DEBUG("hwmon: searching in /sys/class/hwmon");
+
+        std::string sensors = "/sys/class/hwmon/";
+        for (const auto &entry : fs::directory_iterator(sensors)) {
+            auto hwmon_dir = entry.path().string();
+            auto hwmon_name = hwmon_dir + "/name";
+            std::ifstream name_stream(hwmon_name);
+            std::string name_content;
+
+            if (!name_stream.is_open()) {
+                continue;
+            }
+
+            std::getline(name_stream, name_content);
+            name_stream.close();
 
-    auto dir_iterator = fs::directory_iterator(device);
-    auto hwmon = dir_iterator->path().string();
+            if (name_content.find("gpu") == std::string::npos) {
+                continue;
+            }
+
+            // take the first gpu sensor
+            hwmon = hwmon_dir;
+            break;
+        }
+    } else {
+        auto dir_iterator = fs::directory_iterator(device);
+        hwmon = dir_iterator->path().string();
+    }
 
     if (hwmon.empty()) {
         SPDLOG_DEBUG("hwmon: hwmon directory is empty.");