车联网TCU USB的配置和使用

1 usb_composition命令
# cat /sbin/usb/target
# cd /sys/class/android_usb/android0
# cat functions

console shows that QCOM’s default configuration

Usage: usb_composition [Pid] [HSIC] [PERSISTENT] [IMMEDIATE] [FROM_ADBD]
usb_composition 9025 n y y

Then this script will call
/sbin/usb/compositions/$pid n 0.2 $from_adb
ARG1: means path of /sys/class/android_usb/androidX, X = 0 if ARG1 is‘n’
ARG2: delay seconds, for example, sleep 0.2
ARG3: firstly kill adbd and then start adbd when ARG3 is‘n’

2 源代码和编译后的命令路径
USB slave:
system/core/usb/start_usb ---> /etc/rcS.d/S30usb
system/core/usb/usb_composition ---> /sbin/usb_composition
system/core/usb/compositions ---> /sbin/usb/compositions
/sbin/usb/compositions/$PID ---> /sbin/usb/boot_hsusb_composition

adbd:
system/core/adb/start_adbd ---> /etc/init.d/adbd
system/core/adb/adbd ---> /sbin/adbd

bitbake file: oe-core/meta-msm/recipes/system-core/system-core_git.bb

3 Network over USB
QCMAP建立一个桥bridge0（虚拟交换机），ecm0、rndis0或者eth0再attach到这个bridge0上。

echo rndis > /sbin/usb/compositions/usb_net_type
ifconfig
brctl show
route -n

4 Abbreviations
ARC：Argonant RISC Core
AT91SAM9260：SAM means Smart ARM-based Microcontroller
ATMEL SAMBA：ATMEL Smart ARM-based Microcontroller Boot Assistant
DWC2：Design Ware Controller 2，Apple的嵌入式设备，包括iPad和iPhone都是使用的DWC2
ISP1161：Philips' Integrated host Solution Pairs 1161，“Firms introduce USB host controllers”，https://www.eetimes.com/document.asp?doc_id=1290054
Quirks：the attributes of a device that are considered to be noncompliant with expected operation
SL811HS：Cypress/ScanLogic 811 Host/Slave，性能上与ISP1161（Integrated host Solution Pairs 1161）相当
TDI：TransDimension Inc.，该公司首先发明了将TT集成到EHCI RootHub中的方法，这样对于嵌入式系统来说，就省去了OHCI/UHCI的硬件，同时降低了成本，作为对该公司的纪念，Linux内核定义了宏ehci_is_TDI(ehci)；产品UHC124表示USB Host Controller；收购了ARC USB技术；现已被chipidea收购，chipidea又被mips收购
TT：Transaction Translator（事务转换器，将USB2.0的包转换成USB1.1的包）