Add BB information

Author: widgetii

README.md

@@ -151,6 +151,8 @@ Each field is explained as follows:
 
 [Building custom kernel](kernel/build.md)
 
+[Building busybox](busybox/build.md)
+
 ### Debugging
 
 - Debugging on board using gdbserver

busybox/build.md

@@ -0,0 +1,33 @@
+# Building Busybox
+
+```sh
+cd $SDK_DIR/osdrv/opensource/busybox
+tar xvf busybox-1.20.2.tgz
+cd busybox-1.20.2
+make ARCH=arm CROSS_COMPILE=arm-hisiv500-linux- defconfig
+# use in case you need specify custom configuration for Busybox
+# else just skip it:
+make ARCH=arm CROSS_COMPILE=arm-hisiv500-linux- menuconfig
+LDFLAGS="--static" make ARCH=arm CROSS_COMPILE=arm-hisiv500-linux- install CONFIG_PREFIX=./_rootfs
+```
+
+## Building Busybox-only rootfs (Rescue mode)
+
+```sh
+pushd _rootfs
+mkdir -p proc sys dev etc/init.d usr/lib new
+cat <<EOF > etc/init.d/rcS
+#!/bin/sh
+export PATH=/bin:/sbin:/usr/bin:/usr/sbin
+mount -t proc none /proc
+mount -t sysfs none /sys
+/sbin/mdev -s
+EOF
+chmod +x etc/init.d/rcS 
+popd
+
+mksquashfs _rootfs busybox.squash -comp xz
+# get filesize to use it later in kernel params
+stat -c %s busybox.squash
+sudo mv busybox.squash /srv/atftp
+```

reverse/ABI.md

@@ -0,0 +1,8 @@
+# Platform ABI
+
+Only Linux ABI described
+
+|---|---|---|---|
+| Ops | x86 | x86_64 | ARM32 |
+| Registers usage | | | `r0` to `r3`: used to hold argument values passed to a subroutine, and also hold results returned from a subroutine.
+ |

sensors/README.md

@@ -53,3 +53,5 @@ sensor types don't hesitate to make a PR.
 ## Opensource code
 
 - [HiSilison sensor support code from OpenIPC project](https://github.com/ZigFisher/Glutinium/tree/master/hisi-sensors/src)
+
+- [Sensor drivers from Dafang Hacking](https://github.com/EliasKotlyar/Xiaomi-Dafang-Software/tree/master/drivers/sensors)