[SOLVED] How can I create a Bulk USB Gadget WinUSB Device

How can I create a Bulk USB Gadget WinUSB Device

I created an small embedded WinUSB device which offers 2 bulk endpoints. This device can communicate with Linux and with Windows10 without installing driver, or a .inf file.

Now we want to use the same API with a embedded Linux. The USB-Gadget mode offers Serial CDC/ACM and RNDIS-Ethernet and many more.

I was able to create a USB-Gadget with the gadgetfs which had only bulk ep. I could communicate with Linux and Windows host. The USB-Device had /dev/ttyGS0 to communicate. But in Windows I had to install WinUSB driver manually.

I work with yocto to create embedded kernel. I added some line of code here: /linux-imx/drivers/usb/gadget/legacy/serial.c , f_serial.c, u_serial.h to add additional variable os_desc and parameter use_winusb. But the resulting g_serial still creates a COM-Port in Windows10 or a no WinUSB device. For our device we need WinUSB-Device only.

The RNDIS Gadget does has WinUSB support. So I tried to create a own USB-Gadget device with https://github.com/libusbgx/libusbgx. But if I use the USBG_F_SERIAL function type then it can't create WinUSB. See error:

Error setting function OS desc
Error: USBG_ERROR_NOT_FOUND : Not found (file or directory removed)

If I use USBG_F_RNDIS, it works, and with manipulated USB descriptor it'll recognized by Windows as WinUSB device. But Linux implement's it as USB-ETH ethernet device. The USB-Device get's no /dev/ttyGS0 serial connection to communicate.

I'm reading the Linux kernel driver source now, to find the position, where I can simply ann this WinUSB os-descriptor stuff into the USBG_F_SERIAL type. But I think it'll take month to get through.

Any solution would be ok. Patch for the Linux driver sources g_serial or how to configure a USB-Gadgetfs would be great. Any hint, where to put additional code would also be fine.

Solution