From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7D847C4332F for ; Mon, 19 Dec 2022 23:36:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232438AbiLSXgy (ORCPT ); Mon, 19 Dec 2022 18:36:54 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42986 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229853AbiLSXgv (ORCPT ); Mon, 19 Dec 2022 18:36:51 -0500 Received: from netrider.rowland.org (netrider.rowland.org [192.131.102.5]) by lindbergh.monkeyblade.net (Postfix) with SMTP id 94FDCEE37 for ; Mon, 19 Dec 2022 15:36:47 -0800 (PST) Received: (qmail 39912 invoked by uid 1000); 19 Dec 2022 18:36:47 -0500 Date: Mon, 19 Dec 2022 18:36:47 -0500 From: Alan Stern To: dima.pasechnik@cs.ox.ac.uk Cc: Greg KH , linux-usb@vger.kernel.org Subject: Re: usb 1-3: Product: BBC micro:bit CMSIS-DAP not recognised Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org On Mon, Dec 19, 2022 at 10:20:48PM +0000, dima.pasechnik@cs.ox.ac.uk wrote: > On Mon, Dec 19, 2022 at 07:25:03PM +0100, Greg KH wrote: > [...] > > > > That is only if you want to manually bind the generic driver to this > > device. The kernel takes this and says "are you sure you want to do > > this, if so, email this address and talk to these developers" :) > > One does need a dedicated /dev/ttyUSB. It is similar, but not > identical, to /dev/ttyACM. Cf. e.g. > https://rfc1149.net/blog/2013/03/05/what-is-the-difference-between-devttyusbx-and-devttyacmx/ > > And the board makes an effort to establish > a dedicated /dev/ttyUSB. Indeed, after I plugged the board in 21:35 > and did "ls -l /dev/tty*" I saw > > crw--w---- 1 root tty 4, 0 Dec 19 21:28 /dev/tty0 > crw------- 1 dima tty 4, 1 Dec 19 21:35 /dev/tty1 > crw--w---- 1 root tty 4, 10 Dec 19 21:28 /dev/tty10 > crw--w---- 1 root tty 4, 11 Dec 19 21:28 /dev/tty11 > ... > > - it's the Linux host that doesn't recognise this fact. > (it's not even seen in dmesg that something happened on /dev/tty1 - > probably a premature termination of something in the kernel) > > Needless to say, there is also /dev/ttyACM0 popping up - so this part > of the communication is OK. > > I think it's prudent that the kernel understands that it's a > a proper ttyUSB device, apparing as /dev/ttyUSB, and advertises it as > such. Without it, it's hard to detect it, and indeed, the only way I see > this, without an active usbserial driver, is by the time shown next to > /dev/tty* It might help if you post the output of "lsusb -v" for this device. Alan Stern