我有一个 3G 调制解调器 (ZTE MF-210) 作为迷你 pci 子板插入我的平板电脑。
我正在尝试将其集成为我的开源 Android JB 移植项目的一部分：
https://groups.google.com/forum/?fromgroups=#!forum/renesas-emev-osp
因此，我通过添加以下配置选项修改了内核以包含 USB 串行 GSM 调制解调器支持：
CONFIG_USB_SERIAL=y
CONFIG_USB_SERIAL_WWAN=y
CONFIG_USB_SERIAL_OPTION=y
我已经包含了启用 3G 模块电源的代码（由 SoC GPIO 引脚控制）。至少据我所知，这部分看起来很有效。当调制解调器通电时，我在 dmesg 中得到这些日志：
6>usb 1-1.1: new high speed USB device using emxx-ehci-driver and address 9
<6>option 1-1.1:1.0: GSM modem (1-port) converter detected
<7>drivers/usb/serial/usb_wwan.c: usb_wwan_startup
<7>drivers/usb/serial/usb_wwan.c: usb_wwan_setup_urbs
<6>usb 1-1.1: GSM modem (1-port) converter now attached to ttyUSB0
<6>option 1-1.1:1.1: GSM modem (1-port) converter detected
<7>drivers/usb/serial/usb_wwan.c: usb_wwan_startup
<7>drivers/usb/serial/usb_wwan.c: usb_wwan_setup_urbs
<6>usb 1-1.1: GSM modem (1-port) converter now attached to ttyUSB1
<6>option 1-1.1:1.2: GSM modem (1-port) converter detected
<7>drivers/usb/serial/usb_wwan.c: usb_wwan_startup
<7>drivers/usb/serial/usb_wwan.c: usb_wwan_setup_urbs
<6>usb 1-1.1: GSM modem (1-port) converter now attached to ttyUSB2
<6>option 1-1.1:1.3: GSM modem (1-port) converter detected
<7>drivers/usb/serial/usb_wwan.c: usb_wwan_startup
<7>drivers/usb/serial/usb_wwan.c: usb_wwan_setup_urbs
<6>usb 1-1.1: GSM modem (1-port) converter now attached to ttyUSB3
<7>drivers/usb/serial/usb_wwan.c: usb_wwan_open
<7>drivers/usb/serial/usb_wwan.c: usb_wwan_dtr_rts
<7>drivers/usb/serial/usb_wwan.c: usb_wwan_set_termios
<7>drivers/usb/serial/usb_wwan.c: usb_wwan_write_room: 16384
<7>drivers/usb/serial/usb_wwan.c: usb_wwan_write: write (8 chars)
<7>drivers/usb/serial/usb_wwan.c: usb_wwan_write: endpoint 2 buf 0
<7>drivers/usb/serial/usb_wwan.c: usb_wwan_write: wrote (did 8)
<7>drivers/usb/serial/usb_wwan.c: usb_wwan_write_room: 12288
<7>drivers/usb/serial/usb_wwan.c: usb_wwan_write: write (1 chars)
<7>drivers/usb/serial/usb_wwan.c: usb_wwan_write: endpoint 2 buf 1
<7>drivers/usb/serial/usb_wwan.c: usb_wwan_outdat_callback
<7>drivers/usb/serial/usb_wwan.c: usb_wwan_write: wrote (did 1)
<7>drivers/usb/serial/usb_wwan.c: usb_wwan_outdat_callback
<7>drivers/usb/serial/usb_wwan.c: usb_wwan_indat_callback: c78f9640
<7>drivers/usb/serial/usb_wwan.c: usb_wwan_indat_callback: c78f9140
<7>drivers/usb/serial/usb_wwan.c: usb_wwan_indat_callback: c78f90c0
<7>drivers/usb/serial/usb_wwan.c: usb_wwan_write_room: 16384
<7>drivers/usb/serial/usb_wwan.c: usb_wwan_write: write (8 chars)
<7>drivers/usb/serial/usb_wwan.c: usb_wwan_write: endpoint 2 buf 0
<7>drivers/usb/serial/usb_wwan.c: usb_wwan_write: wrote (did 8)
...
请注意，我在 usb_wwan.c 中启用了调试
我在文件系统上得到以下信息：
# ls -l /dev/ttyUSB*
crw-rw---- radio radio 188, 0 2013-05-22 15:50 ttyUSB0
crw-rw---- radio radio 188, 1 2013-05-22 15:51 ttyUSB1
crw-rw---- radio radio 188, 2 2013-05-22 15:50 ttyUSB2
crw------- root root 188, 3 2013-05-22 15:50 ttyUSB3
# cat /proc/tty/driver/usbserial
usbserinfo:1.0 driver:2.0
0: name:"GSM modem (1-port)" vendor:19d2 product:2003 num_ports:1 port:1 path:usb-emxx_ehci-1.1
1: name:"GSM modem (1-port)" vendor:19d2 product:2003 num_ports:1 port:1 path:usb-emxx_ehci-1.1
2: name:"GSM modem (1-port)" vendor:19d2 product:2003 num_ports:1 port:1 path:usb-emxx_ehci-1.1
3: name:"GSM modem (1-port)" vendor:19d2 product:2003 num_ports:1 port:1 path:usb-emxx_ehci-1.1
根据我在网上找到的一些信息（例如http://blog.csdn.net/vishtvro/article/details/7505915；我不确定如何直接验证，因为我没有 'lsusb -v ' 在 Android 操作系统上，busybox 没有帮助），四个端口对应于：
ttyUSB3: Modem
ttyUSB1: AT
ttyUSB0: Debug
ttyUSB2: VoUSB
问题是我无法使用“picocom”或“busybox microcom”与这些端口通信。我可以连接到它，但不能发送或接收命令：
# picocom /dev/ttyUSB1 -b 115200
picocom v1.6
port is : /dev/ttyUSB1
flowcontrol : none
baudrate is : 115200
parity is : none
databits are : 8
escape is : C-a
local echo is : no
noinit is : no
noreset is : no
nolock is : no
send_cmd is : sz -vv
receive_cmd is : rz -vv
imap is :
omap is :
emap is : crcrlf,delbs,
Terminal ready
<blinking cursor here>
在 usb_wwan.c 调试日志中报告键入字符，例如
<7>drivers/usb/serial/usb_wwan.c: usb_wwan_chars_in_buffer: 0
<7>drivers/usb/serial/usb_wwan.c: usb_wwan_write_room: 16384
<7>drivers/usb/serial/usb_wwan.c: usb_wwan_chars_in_buffer: 0
<7>drivers/usb/serial/usb_wwan.c: usb_wwan_write_room: 16384
<7>drivers/usb/serial/usb_wwan.c: usb_wwan_write: write (1 chars)
<7>drivers/usb/serial/usb_wwan.c: usb_wwan_write: endpoint 1 buf 0
<7>drivers/usb/serial/usb_wwan.c: usb_wwan_write: wrote (did 1)
<7>drivers/usb/serial/usb_wwan.c: usb_wwan_chars_in_buffer: 1
<7>drivers/usb/serial/usb_wwan.c: usb_wwan_write_room: 12288
<7>drivers/usb/serial/usb_wwan.c: usb_wwan_outdat_callback
但它不会在控制台上回显，如果我键入任何 AT 命令，我也不会得到任何结果。'AT' 应该返回 'OK' - 这是我的基本期望，但我什么也没看到。
我在网上和 stackexchange 上搜索了很长时间，但直到现在都找不到任何有用的提示。
有关如何调试此问题的任何建议？
注意 - 在库存 GB Android 固件上，调制解调器按预期工作 - 不幸的是我没有那个 GB 代码......
提前致谢！