Merge "evemu-record: add README" into main

Author: HarryCutts

cmds/evemu-record/README.md

@@ -0,0 +1,48 @@
+# `evemu-record`
+
+This is a Rust implementation of the `evemu-record` command from the [FreeDesktop project's evemu
+suite][FreeDesktop]. It records the descriptor and events produced by a single input device in a
+[simple text-based format][format] that can be replayed using the [`uinput` command on
+Android][uinput] or the FreeDesktop evemu tools on other Linux-based platforms. It is included by
+default with `userdebug` and `eng` builds of Android.
+
+The command-line interface is the same as that of the FreeDesktop version, except for
+Android-specific features. For usage instructions, run `evemu-record --help`.
+
+## Usage example
+
+From a computer connected to the device over ADB, you can start a recording:
+
+```
+$ adb shell evemu-record > my-recording.evemu
+Available devices:
+/dev/input/event0:      gpio_keys
+/dev/input/event1:      s2mpg12-power-keys
+/dev/input/event2:      NVTCapacitiveTouchScreen
+/dev/input/event3:      NVTCapacitivePen
+/dev/input/event4:      uinput-folio
+/dev/input/event5:      ACME Touchpad
+Select the device event number [0-5]: 5
+```
+
+...then use the input device for a while, and press Ctrl+C to finish. You will now have a
+`my-recording.evemu` file that you can examine in a text editor. To replay it, use the [`uinput`
+command][uinput]:
+
+```
+$ adb shell uinput - < my-recording.evemu
+```
+
+## Android-specific features
+
+### Timestamp bases
+
+By default, event timestamps are recorded relative to the time of the first event received during
+the recording. Passing `--timestamp-base=boot` causes the timestamps to be recorded relative to the
+system boot time instead. While this does not affect the playback of the recording, it can be useful
+for matching recorded events with other logs that use such timestamps, such as `dmesg` or the
+touchpad gesture debug logs emitted by `TouchpadInputMapper`.
+
+[FreeDesktop]: https://gitlab.freedesktop.org/libevdev/evemu
+[format]: https://gitlab.freedesktop.org/libevdev/evemu#device-description-format
+[uinput]: https://cs.android.com/android/platform/superproject/main/+/main:frameworks/base/cmds/uinput/README.md