复合USB CDC小工具不适用于Windows主机 [英] Composite USB CDC Gadget doesn't work with Windows hosts

问题描述

我有一个带USB设备接口的嵌入式Linux 3.19系统。设备需要向主机公开三个USB接口：一个虚拟网络接口(RNDIS或CDC ECM)和两个虚拟串行端口(CDC ACM)。该设备需要与现代Windows(7+)和Linux(3.16+)主机协作。

鉴于Windows本身不支持CDC ECM，我们决定实现两种USB配置(这是一种流行的方法)：

• 配置1，接口如下：
  • RNDIS
  • CDC ACM 0
  • CDC ACM 1
• 配置2，接口如下：
  • CDC ECM
  • CDC ACM 0
  • CDC ACM 1

目的是让Windows将本机支持的第一个配置与RNDIS一起使用(Windows始终选择第一个USB配置)；并让非Windows主机将第二个配置与CDC ECM一起使用。

我编写了一个脚本(基于David Lechner的类似脚本)：http://pastebin.com/VtAusEmf。下面提供了脚本的相关部分(请点击链接查看完整的脚本，比较大)：

mkdir -p ${g}
echo "${usb_ver}" > ${g}/bcdUSB
echo "${dev_class}" > ${g}/bDeviceClass
echo "${vid}" > ${g}/idVendor
echo "${pid}" > ${g}/idProduct
mkdir ${g}/strings/0x409
echo "${mfg}" > ${g}/strings/0x409/manufacturer
echo "${prod}" > ${g}/strings/0x409/product
echo "${serial}" > ${g}/strings/0x409/serialnumber

mkdir ${g}/configs/c.1
echo "${attr}" > ${g}/configs/c.1/bmAttributes
echo "${pwr}" > ${g}/configs/c.1/MaxPower
mkdir ${g}/configs/c.1/strings/0x409
echo "${cfg1}" > ${g}/configs/c.1/strings/0x409/configuration

echo "1" > ${g}/os_desc/use
echo "${ms_vendor_code}" > ${g}/os_desc/b_vendor_code
echo "${ms_qw_sign}" > ${g}/os_desc/qw_sign

mkdir ${g}/functions/rndis.usb0
echo "${dev_mac}" > ${g}/functions/rndis.usb0/dev_addr
echo "${host_mac}" > ${g}/functions/rndis.usb0/host_addr
echo "${ms_compat_id}" > ${g}/functions/rndis.usb0/os_desc/interface.rndis/compatible_id
echo "${ms_subcompat_id}" > ${g}/functions/rndis.usb0/os_desc/interface.rndis/sub_compatible_id

mkdir ${g}/configs/c.2
echo "${attr}" > ${g}/configs/c.2/bmAttributes
echo "${pwr}" > ${g}/configs/c.2/MaxPower
mkdir ${g}/configs/c.2/strings/0x409
echo "${cfg2}" > ${g}/configs/c.2/strings/0x409/configuration

mkdir ${g}/functions/ecm.usb0
echo "${dev_mac}" > ${g}/functions/ecm.usb0/dev_addr
echo "${host_mac}" > ${g}/functions/ecm.usb0/host_addr

mkdir ${g}/functions/acm.GS0
mkdir ${g}/functions/acm.GS1

ln -s ${g}/configs/c.1          ${g}/os_desc
ln -s ${g}/functions/rndis.usb0 ${g}/configs/c.1
ln -s ${g}/functions/acm.GS0    ${g}/configs/c.1
ln -s ${g}/functions/acm.GS1    ${g}/configs/c.1
ln -s ${g}/functions/ecm.usb0   ${g}/configs/c.2
ln -s ${g}/functions/acm.GS0    ${g}/configs/c.2
ln -s ${g}/functions/acm.GS1    ${g}/configs/c.2

echo "${device}" > ${g}/UDC

生成的Gadget配置在Linux主机上运行良好(选择第二个配置，所有三个接口均可用并正常工作)，但Windows主机(使用8和10进行测试)仅检测RNDIS接口，而忽略ACM接口。不过，RNDIS运行良好。

如果禁用RNDIS接口，Windows主机将仅检测第一个ACM接口，忽略第二个。

我怀疑Windows无法正确处理复合USB设备。是这样，还是我做错了什么？如果是，我是否必须编写自己的.inf文件，指定需要加载哪些类驱动程序？

推荐答案

rtfm有帮助。有关复合USB设备的要求，请参阅以下文章：

• https://docs.microsoft.com/en-us/windows-hardware/drivers/usbcon/enumeration-of-the-composite-parent-device
• https://docs.microsoft.com/en-us/windows-hardware/drivers/usbcon/usb-interface-association-descriptor
• https://docs.microsoft.com/en-us/windows-hardware/drivers/usbcon/supported-usb-classes

解决方案：

echo "0xEF" > ${g}/bDeviceClass
echo "0x02" > ${g}/bDeviceSubClass
echo "0x01" > ${g}/bDeviceProtocol

这篇关于复合USB CDC小工具不适用于Windows主机的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！