drm_hwcomposer: Add test utility to listen for uevents

Dumping uevents is useful for debugging purposes.

1. Extract logic related to uevent socket into utils/UEvent.h class.
2. Use it by both UEventListener.cpp and tests/uevent_print.cpp.

Bump clang-tidy level of UEventListener.cpp to normal.

Signed-off-by: Roman Stratiienko <roman.o.stratiienko@globallogic.com>

utils/UEvent.h

@@ -0,0 +1,85 @@
+/*
+ * Copyright (C) 2022 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#pragma once
+
+#include <linux/netlink.h>
+#include <sys/socket.h>
+
+#include <cerrno>
+#include <memory>
+#include <optional>
+#include <string>
+
+#include "UniqueFd.h"
+#include "log.h"
+
+namespace android {
+
+class UEvent {
+ public:
+  static auto CreateInstance() -> std::unique_ptr<UEvent> {
+    auto fd = UniqueFd(
+        socket(PF_NETLINK, SOCK_DGRAM | SOCK_CLOEXEC, NETLINK_KOBJECT_UEVENT));
+
+    if (!fd) {
+      ALOGE("Failed to open uevent socket: errno=%i", errno);
+      return {};
+    }
+
+    struct sockaddr_nl addr {};
+    addr.nl_family = AF_NETLINK;
+    addr.nl_pid = 0;
+    addr.nl_groups = UINT32_MAX;
+
+    // NOLINTNEXTLINE(cppcoreguidelines-pro-type-cstyle-cast)
+    int ret = bind(fd.Get(), (struct sockaddr *)&addr, sizeof(addr));
+    if (ret != 0) {
+      ALOGE("Failed to bind uevent socket: errno=%i", errno);
+      return {};
+    }
+
+    return std::unique_ptr<UEvent>(new UEvent(fd));
+  }
+
+  auto ReadNext() -> std::optional<std::string> {
+    constexpr int kUEventBufferSize = 1024;
+    char buffer[kUEventBufferSize];
+    ssize_t ret = 0;
+    ret = read(fd_.Get(), &buffer, sizeof(buffer));
+    if (ret == 0)
+      return {};
+
+    if (ret < 0) {
+      ALOGE("Got error reading uevent %zd", ret);
+      return {};
+    }
+
+    for (int i = 0; i < ret - 1; i++) {
+      if (buffer[i] == '\0') {
+        buffer[i] = '\n';
+      }
+    }
+
+    return std::string(buffer);
+  }
+
+ private:
+  explicit UEvent(UniqueFd &fd) : fd_(std::move(fd)){};
+  UniqueFd fd_;
+};
+
+}  // namespace android