From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753440AbdBAQ7a (ORCPT ); Wed, 1 Feb 2017 11:59:30 -0500 Received: from mail.kmu-office.ch ([178.209.48.109]:41900 "EHLO mail.kmu-office.ch" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753130AbdBAQ72 (ORCPT ); Wed, 1 Feb 2017 11:59:28 -0500 MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Date: Wed, 01 Feb 2017 08:59:18 -0800 From: Stefan Agner To: Greg KH Cc: balbi@kernel.org, andrzej.p@samsung.com, linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/2] fs: configfs: make qw_sign attribute symmetric In-Reply-To: <20170201080616.GA17968@kroah.com> References: <20170201021917.27398-1-stefan@agner.ch> <20170201080616.GA17968@kroah.com> Message-ID: User-Agent: Roundcube Webmail/1.1.3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2017-02-01 00:06, Greg KH wrote: > On Tue, Jan 31, 2017 at 06:19:16PM -0800, Stefan Agner wrote: >> Currently qw_sign requires UTF-8 character to set, but returns UTF-16 >> when read. This isn't obvious when simply using cat since the null >> characters are not visible, but hexdump unveils the true string: >> >> # echo MSFT100 > os_desc/qw_sign >> # hexdump -C os_desc/qw_sign >> 00000000 4d 00 53 00 46 00 54 00 31 00 30 00 30 00 |M.S.F.T.1.0.0.| >> >> Make qw_sign symmetric by returning an UTF-8 string too. Also follow >> common convention and add a new line at the end. > > Doesn't USB require that strings be in UTF-16? So why have the kernel > convert them? That is a discussion we should have had when the write side of this has been added: static ssize_t os_desc_qw_sign_store(struct config_item *item, const char *page, size_t len) { struct gadget_info *gi = os_desc_item_to_gadget_info(item); int res, l; l = min((int)len, OS_STRING_QW_SIGN_LEN >> 1); if (page[l - 1] == '\n') --l; mutex_lock(&gi->lock); res = utf8s_to_utf16s(page, l, UTF16_LITTLE_ENDIAN, (wchar_t *) gi->qw_sign, OS_STRING_QW_SIGN_LEN); if (res > 0) res = len; mutex_unlock(&gi->lock); return res; } The store function is definitely already in use today, e.g. this script used for ev3dev: https://github.com/ev3dev/ev3-systemd/blob/ev3dev-jessie/scripts/ev3-usb.sh Changing it to UTF-16 would break that script... So changing the store part is the lesser of two evils. Regarding new line: Just following what other attributes are doing by using the GS_STRINGS_R macro. -- Stefan