高通modem 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 源代碼和編譯後的命令路徑
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 Abbreviations
ARC：Argonant RISC Core
AT91SAM9260：SAM means Smart ARM-based Microcontroller
ATMEL SAMBA：ATMEL Smart ARM-based Microcontroller Boot Assistant
CC2530：TI ChipCon2530
DWC2：Design Ware Controller 2，Apple的嵌入式設備，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，性能上與ISP1161（Integrated host Solution Pairs 1161）相當
TDI：TransDimension Inc.，該公司首先發明瞭將TT集成到EHCI RootHub中的方法，這樣對於嵌入式系統來說，就省去了OHCI/UHCI的硬件，同時降低了成本，作爲對該公司的紀念，Linux內核定義了宏ehci_is_TDI(ehci)；產品UHC124表示USB Host Controller；收購了ARC USB技術；現已被chipidea收購，chipidea又被mips收購
TLV：TI Low Value，高性價比
TPS：TI Performance Solution
TT：Transaction Translator（事務轉換器，將USB2.0的包轉換成USB1.1的包）