Currently I am stuck trying to retrieve the version of the chip, which seems to be needed to configure it slightly different later on. FreeBSD function https://github.com/freebsd/freebsd/blob/f6abce8e79ecc1992d2d0b2e53f8e92ab3102671/sys/dev/usb/serial/uchcom.c#L479, which calls a different function to read data into a buffer from the device.
A similar function is also present for writing, based on ftdi and pl2303 I managed to get the write function to work (I think, it returns USB_SUCCESS).
However I cannot get the read function to work, It returns USB_FAILURE with CR set to Endpoint returned stall PID
static int
uchcom_cmd_vendor_write0(uchcom_state_t *uch,