beluga: initrdscripts: Provide a means to access ADB from the boot image

This change is analogous to https://github.com/AsteroidOS/meta-smartwatch/pull/254/files.
However, on `beluga` only the bottom right button is sending an event so this is used.

Signed-off-by: Darrel Griët <[email protected]>

meta-beluga/recipes-core/initrdscripts/initramfs-scripts-android/init.machine.sh

@@ -2,19 +2,10 @@
 
 BOOT_DIR=$1
 
-# Manually mount the system partition as it contains the boot image (ramdisk) as well as the system data (under /system/system).
-mkdir -m 0777 $BOOT_DIR/boot
-mount -t auto -o ro /dev/mmcblk0p36 $BOOT_DIR/boot
 
-# Allow Android binaries to load libraries from /usr/libexec/ (for example /usr/libexec/hal-droid/system/lib/libselinux_stubs.so)
-mount --bind /ld.config.28.txt $BOOT_DIR/boot/system/etc/ld.config.28.txt
-
-# Make the 'system' folder available as the system partition to the rootfs.
-ln -s /boot/system/ $BOOT_DIR/system
-
-# Check if the AsteroidOS specific machine configuration file exists.
-# If it doesn't then we know that the userdata partition is mounted but doesn't contain a valid AsteroidOS root.
-if [ ! -e $BOOT_DIR/etc/asteroid/machine.conf ] ; then
+# Start the ADB daemon
+startadbd() {
+    trap - SIGUSR1
     echo MSG "Push asteroidos.ext4 via ADB" > /run/psplash_fifo
 
     # Setup for use with ConfigFS
@@ -27,4 +18,43 @@ if [ ! -e $BOOT_DIR/etc/asteroid/machine.conf ] ; then
     echo OPPO Watch > /sys/kernel/config/usb_gadget/g1/strings/0x409/product
 
     /usr/bin/adbd
+}
+
+# wait for the middle button to be pressed, and if it is,
+# kill the calling process group with SIGUSR1
+# The format of these events is documented here:
+# https://github.com/torvalds/linux/blob/master/include/uapi/linux/input.h#L28-L47
+# u32 - tv_sec
+# u32 - tv_usec
+# u16 - type
+# u16 - code
+# s32 - value
+# On this watch the bottom button has a type of 2ee
+# The top button is encoded in a different event.
+waitmidbutton() {
+    fmtstring='1/4 "%d." 1/4 "%d\t" 1/2 "%2x\t" 1/2 "%2x\t" 1/4 "%u\n"'
+    result=$(hexdump -n16 -e "${fmtstring}" /dev/input/event0 | cut -f3 -)
+    if [ ${result} == 2ee ] ; then kill -s USR1 $1 ; fi
+}
+
+# Manually mount the system partition as it contains the boot image (ramdisk) as well as the system data (under /system/system).
+mkdir -m 0777 $BOOT_DIR/boot
+mount -t auto -o ro /dev/mmcblk0p36 $BOOT_DIR/boot
+
+# Allow Android binaries to load libraries from /usr/libexec/ (for example /usr/libexec/hal-droid/system/lib/libselinux_stubs.so)
+mount --bind /ld.config.28.txt $BOOT_DIR/boot/system/etc/ld.config.28.txt
+
+# Make the 'system' folder available as the system partition to the rootfs.
+ln -s /boot/system/ $BOOT_DIR/system
+
+# Check if the AsteroidOS specific machine configuration file exists.
+# If it doesn't then we know that the userdata partition is mounted but doesn't contain a valid AsteroidOS root.
+if [ ! -e $BOOT_DIR/etc/asteroid/machine.conf ] ; then
+    startadbd
+else
+# wait for either 5 seconds or for the user to hit the middle button
+# If the timout expires, the watch boots normally; otherwise it starts ADB daemon
+    trap "startadbd" SIGUSR1
+    waitmidbutton $$ &
+    sleep 5
 fi