platform_bootable_recovery/minadbd/README.md
Tao Bao 0cc2c5b453 minadbd: Update README.md.
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2019-09-27 13:17:16 -07:00

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minadbd
=======
`minadbd` is analogous to the regular `adbd`, but providing the minimal services to support
recovery-specific use cases. Generally speaking, `adbd` = `libadbd` + `libadbd_services`, whereas
`minadbd` = `libadbd` + `libminadbd_services`.
Although both modules may be installed into the recovery image, only one of them, or none, can be
active at any given time.
- The start / stop of `adbd` is managed via system property `sys.usb.config`, when setting to `adb`
or `none` respectively. Upon starting recovery mode, `adbd` is started in debuggable builds by
default; otherwise `adbd` will stay off at all times in user builds. See the triggers in
`bootable/recovery/etc/init.rc`.
- `minadbd` is started by `recovery` as needed.
- When requested to start `minadbd`, `recovery` stops `adbd` first, if it's running; it then forks
and execs `minadbd` in a separate process.
- `minadbd` talks to host-side `adb` server to get user requests.
- `minadbd` handles some requests directly, e.g. querying device properties for rescue service.
- `minadbd` communicates with `recovery` to fulfill requests regarding package installation. See
the comments in `bootable/recovery/install/adb_install.cpp` for the IPC protocol between
`recovery` and `minadbd`.
- Upon exiting `minadbd`, `recovery` restarts `adbd` if it was previously running.