On Tue, 21 May 2019, Eric W. Biederman wrote: > Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> writes: > >> req = (struct usb_ctrlrequest *) buf; > >> req->bRequestType = USB_DIR_IN | USB_TYPE_STANDARD | USB_RECIP_DEVICE; > >> req->bRequest = USB_REQ_GET_DESCRIPTOR; > >> req->wValue = htole16(USB_DT_DEVICE << 8); > >> req->wIndex = htole16(0); > >> req->wLength = htole16(sizeof(buf) - sizeof(*req)); > > > > In fact, these values are supposed to be in host-endian order, not > > necessarily little-endian. The USB core converts them if necessary. > > Please look again. In include/uapi/linux/ch9.h those fields are > explicitly defined as little endian and the code in devio.c for > USBDEVFS_URB_TYPE_CONTROL treats them as little endian. Perhaps there > is a mismatch here but I haven't seen it and I needed this change to get > the code to work on big endian. Oops -- you're right. I was thinking of the USBDEVFS_CONTROL ioctl. Sorry for the mistake. Alan Stern
