Merge "minadbd: Update README.md."
am: ec734e5851
Change-Id: I133418ea66cce3fdb70c3baba7fa8d6b68beb740
diff --git a/minadbd/README.md b/minadbd/README.md
index 5a0a067..9a19583 100644
--- a/minadbd/README.md
+++ b/minadbd/README.md
@@ -1,8 +1,24 @@
-minadbd is now mostly built from libadbd. The fuse features are unique to
-minadbd, and services.c has been modified as follows:
+minadbd
+=======
- - all services removed
- - all host mode support removed
- - `sideload_service()` added; this is the only service supported. It
- receives a single blob of data, writes it to a fixed filename, and
- makes the process exit.
+`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.