session_manager_lib/
power.rs

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1// Copyright 2024 The Fuchsia Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5use anyhow::{anyhow, Context};
6use fidl::endpoints::{ClientEnd, Proxy};
7use power_broker_client::{basic_update_fn_factory, run_power_element, PowerElementContext};
8use rand::distributions::Alphanumeric;
9use rand::Rng;
10use std::sync::Arc;
11use {
12    fidl_fuchsia_power_broker as fbroker, fidl_fuchsia_power_system as fsystem,
13    fuchsia_async as fasync,
14};
15
16/// A power element representing the session.
17///
18/// This power element is owned and registered by `session_manager`. This power element is
19/// added in the power topology as a dependent on the Application Activity element that is
20/// owned by the SAG.
21///
22/// After `session_manager` starts, a power-on lease will be created and retained.
23/// The session component may fetch the lease from `session_manager` and decide when to
24/// drop it.
25///
26/// When stopping or restarting the session, the power element and the power-on lease will
27/// be recreated, returning thing to the initial started state.
28pub struct PowerElement {
29    // Keeps the element alive.
30    #[allow(dead_code)]
31    power_element_context: Arc<PowerElementContext>,
32
33    /// The first lease on the power element.
34    lease: Option<ClientEnd<fbroker::LeaseControlMarker>>,
35}
36
37/// The power levels defined for the session manager power element.
38///
39/// | Power Mode        | Level |
40/// | ----------------- | ----- |
41/// | On                | 1     |
42/// | Off               | 0     |
43///
44static POWER_ON_LEVEL: fbroker::PowerLevel = 1;
45
46impl PowerElement {
47    /// # Panics
48    /// If internal invariants about the state of the `lease` field are violated.
49    pub async fn new() -> Result<Self, anyhow::Error> {
50        let topology = fuchsia_component::client::connect_to_protocol::<fbroker::TopologyMarker>()?;
51        let activity_governor =
52            fuchsia_component::client::connect_to_protocol::<fsystem::ActivityGovernorMarker>()?;
53
54        // Create the PowerMode power element depending on the Execution State of SAG.
55        let power_elements = activity_governor
56            .get_power_elements()
57            .await
58            .context("cannot get power elements from SAG")?;
59        let Some(Some(application_activity_token)) = power_elements
60            .application_activity
61            .map(|application_activity| application_activity.assertive_dependency_token)
62        else {
63            return Err(anyhow!("Did not find application activity assertive dependency token"));
64        };
65
66        // TODO(https://fxbug.dev/316023943): also depend on execution_resume_latency after implemented.
67        let power_levels: Vec<u8> = (0..=POWER_ON_LEVEL).collect();
68        let random_string: String =
69            rand::thread_rng().sample_iter(&Alphanumeric).take(8).map(char::from).collect();
70        let power_element_context = Arc::new(
71            PowerElementContext::builder(
72                &topology,
73                format!("session-manager-element-{random_string}").as_str(),
74                &power_levels,
75            )
76            .initial_current_level(POWER_ON_LEVEL)
77            .dependencies(vec![fbroker::LevelDependency {
78                dependency_type: fbroker::DependencyType::Assertive,
79                dependent_level: POWER_ON_LEVEL,
80                requires_token: application_activity_token,
81                requires_level_by_preference: vec![
82                    fsystem::ApplicationActivityLevel::Active.into_primitive()
83                ],
84            }])
85            .build()
86            .await
87            .map_err(|e| anyhow!("PowerBroker::AddElementError({e:?}"))?,
88        );
89        let pe_context = power_element_context.clone();
90        fasync::Task::local(async move {
91            run_power_element(
92                pe_context.name(),
93                &pe_context.required_level,
94                POWER_ON_LEVEL, /* initial_level */
95                None,           /* inspect_node */
96                basic_update_fn_factory(&pe_context),
97            )
98            .await;
99        })
100        .detach();
101
102        // Power on by holding a lease.
103        let lease = power_element_context
104            .lessor
105            .lease(POWER_ON_LEVEL)
106            .await?
107            .map_err(|e| anyhow!("PowerBroker::LeaseError({e:?})"))?;
108
109        // Wait for the lease to be satisfied.
110        let lease = lease.into_proxy();
111        let mut status = fbroker::LeaseStatus::Unknown;
112        loop {
113            match lease.watch_status(status).await? {
114                fbroker::LeaseStatus::Satisfied => break,
115                new_status => status = new_status,
116            }
117        }
118        let lease = lease
119            .into_client_end()
120            .expect("Proxy should be in a valid state to convert into client end");
121
122        let boot_control =
123            fuchsia_component::client::connect_to_protocol::<fsystem::BootControlMarker>()?;
124        let () = boot_control.set_boot_complete().await?;
125
126        Ok(Self { power_element_context, lease: Some(lease) })
127    }
128
129    pub fn take_lease(&mut self) -> Option<ClientEnd<fbroker::LeaseControlMarker>> {
130        self.lease.take()
131    }
132
133    pub fn has_lease(&self) -> bool {
134        self.lease.is_some()
135    }
136}
session_manager_lib/power.rs

session_manager_lib/
power.rs
