power_monitor: add powerd client

This Cl adds powerd client in powerd module. The power client is a
blocking client that serves to send dbus request to powerd and receive
response. Currently, only GetPowerSupplyProperties dbus request is
supported. The GetPowerSupplyProperties will be used in following CLs.

BUG=b:361281568
TEST=cargo build --features=power-monitor-powerd

Change-Id: I5e9714bdd10ac3d5906995dfa35c34dd360f4567
Reviewed-on: https://chromium-review.googlesource.com/c/crosvm/crosvm/+/5915194
Reviewed-by: Keiichi Watanabe <keiichiw@chromium.org>
Reviewed-by: Daniel Verkamp <dverkamp@chromium.org>
Commit-Queue: Yuan Yao <yuanyaogoog@chromium.org>

Cargo.lock

@@ -2259,6 +2259,7 @@ dependencies = [
  "proto_build_tools",
  "protobuf",
  "remain",
+ "system_api",
  "thiserror",
 ]
 

power_monitor/Cargo.toml

@@ -12,6 +12,7 @@ base = { path = "../base" }
 dbus = { version = "0.9", optional = true }
 protobuf = "3.2"
 remain = "0.2"
+system_api = { path = "../system_api"}
 thiserror = "1.0.20"
 
 [build-dependencies]

power_monitor/src/lib.rs

@@ -12,6 +12,10 @@ pub trait PowerMonitor: ReadNotifier {
     fn read_message(&mut self) -> std::result::Result<Option<PowerData>, Box<dyn Error>>;
 }
 
+pub trait PowerClient {
+    fn get_power_data(&mut self) -> std::result::Result<PowerData, Box<dyn Error>>;
+}
+
 pub struct PowerData {
     pub ac_online: bool,
     pub battery: Option<BatteryData>,

power_monitor/src/powerd.rs

@@ -14,7 +14,10 @@ use crate::PowerData;
 
 // Interface name from power_manager/dbus_bindings/org.chromium.PowerManager.xml.
 pub const POWER_INTERFACE_NAME: &str = "org.chromium.PowerManager";
+// Object path from power_manager/dbus_bindings/org.chromium.PowerManager.xml.
+pub const POWER_OBJECT_PATH: &str = "/org/chromium/PowerManager";
 
+pub mod client;
 pub mod monitor;
 
 impl From<PowerSupplyProperties> for PowerData {

power_monitor/src/powerd/client.rs

@@ -0,0 +1,71 @@
+// Copyright 2024 The ChromiumOS Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+//! Dbus client for sending request to powerd to get power properties.
+
+use std::error::Error;
+use std::time::Duration;
+
+use dbus::blocking::Connection;
+use protobuf::Message;
+use remain::sorted;
+use system_api::client::OrgChromiumPowerManager;
+use thiserror::Error;
+
+use crate::powerd::POWER_INTERFACE_NAME;
+use crate::powerd::POWER_OBJECT_PATH;
+use crate::protos::power_supply_properties::PowerSupplyProperties;
+use crate::PowerClient;
+use crate::PowerData;
+
+// 25 seconds is the default timeout for dbus-send.
+const DEFAULT_DBUS_TIMEOUT: Duration = Duration::from_secs(25);
+
+pub struct DBusClient {
+    connection: Connection,
+}
+
+#[sorted]
+#[derive(Error, Debug)]
+pub enum DBusClientError {
+    #[error("failed to convert protobuf message: {0}")]
+    ConvertProtobuf(protobuf::Error),
+    #[error("failed to connect to D-Bus: {0}")]
+    DBusConnect(dbus::Error),
+    #[error("failed to read D-Bus message: {0}")]
+    DBusRead(dbus::Error),
+}
+
+impl DBusClient {
+    /// Creates a new blocking dbus connection to system bus.
+    pub fn connect() -> std::result::Result<Box<dyn PowerClient>, Box<dyn Error>> {
+        let channel = dbus::channel::Channel::get_private(dbus::channel::BusType::System)
+            .map_err(DBusClientError::DBusConnect)?;
+
+        let connection = dbus::blocking::Connection::from(channel);
+
+        Ok(Box::new(Self { connection }))
+    }
+}
+
+// Send GetPowerSupplyProperties dbus request to power_manager(powerd), blocks until it gets
+// response, and converts the response into PowerData.
+impl PowerClient for DBusClient {
+    fn get_power_data(&mut self) -> std::result::Result<PowerData, Box<dyn Error>> {
+        let proxy = self.connection.with_proxy(
+            POWER_INTERFACE_NAME,
+            POWER_OBJECT_PATH,
+            DEFAULT_DBUS_TIMEOUT,
+        );
+        let data_bytes = proxy
+            .get_power_supply_properties()
+            .map_err(DBusClientError::DBusRead)?;
+        let mut props = PowerSupplyProperties::new();
+        props
+            .merge_from_bytes(&data_bytes)
+            .map_err(DBusClientError::ConvertProtobuf)?;
+        let data: PowerData = props.into();
+        Ok(data)
+    }
+}