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dbus

README.md

src/chromeos/dbus

This directory contains client libraries for communication with Chrome OS system service daemons over D-Bus.

For more information, see Chrome OS D-Bus Usage in Chrome.

D-Bus Client Best Practices

An example of a relatively simple client using existing patterns can be found in src/chromeos/dbus/dlp.

  • Create a subdirectory under src/chromeos/dbus for new clients or use an existing directory. If a new client is ash-specific, create a subdirectory under src/chromeos/ash/components/dbus. Do not add new clients to this directory. If Lacros wants to talk to D-Bus service, the default recommendation is to build a crosapi class in ash proxying requests to the D-Bus service, then let lacros talk to ash. If you need direct communication from lacros to the D-Bus service, please be consulted by lacros-team@.

  • D-Bus clients are explicitly initialized and shut down. They provide a static getter for the single global instance. In Ash Chrome, initialization occurs in ash_dbus_helper.cc. In Lacros Chrome, initialization occurs in lacros_dbus_helper.cc.

  • Be careful when providing access to multiple processes (e.g. Ash Chrome and Lacros Chrome). Not all of the underlying daemons support multiple clients.

  • For new clients, if test methods are required, create a TestInterface in the base class with a virtual GetTestInterface() method and implement it only in the fake (return null in the real implementation). See src/chromeos/dbus/dlp for an example.

    (Many existing clients provide additional test functionality in the fake implementation, however this complicates tests and the fake implementation).

  • These clients do not have any dependency on FeatureList, and care should be taken regarding initialization order if such dependencies are added (see BluezDBusManager for an example of such client).

Older clients that have been removed:

  • Amplifier (amplifier_client.cc)
  • Audio DSP (audio_dsp_client.cc)
  • Introspection (introspectable_client.cc)
  • NFC (nfc_manager_client.cc)
  • peerd (peer_daemon_manager_client.cc)
  • privetd (privet_daemon_manager_client.cc)
  • Wi-Fi AP manager (ap_manager_client.cc)