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 X-Spam-Level: X-Spam-Status: No, score=-5.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 167C5C4338F for ; Sat, 14 Aug 2021 01:45:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EE8E76103A for ; Sat, 14 Aug 2021 01:45:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236394AbhHNBpr (ORCPT ); Fri, 13 Aug 2021 21:45:47 -0400 Received: from netrider.rowland.org ([192.131.102.5]:52259 "HELO netrider.rowland.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S236289AbhHNBpr (ORCPT ); Fri, 13 Aug 2021 21:45:47 -0400 Received: (qmail 56475 invoked by uid 1000); 13 Aug 2021 21:45:18 -0400 Date: Fri, 13 Aug 2021 21:45:18 -0400 From: Alan Stern To: Maxim Devaev Cc: balbi@kernel.org, gregkh@linuxfoundation.org, ruslan.bilovol@gmail.com, mika.westerberg@linux.intel.com, maze@google.com, jj251510319013@gmail.com, linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] usb: gadget: f_hid: optional SETUP/SET_REPORT mode Message-ID: <20210814014518.GA56183@rowland.harvard.edu> References: <20210813114551.72898-1-mdevaev@gmail.com> <20210813145823.GA38198@rowland.harvard.edu> <20210813232212.5cba6d33@reki> <20210813234022.5d5644ae@reki> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20210813234022.5d5644ae@reki> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org On Fri, Aug 13, 2021 at 11:40:22PM +0300, Maxim Devaev wrote: > В Fri, 13 Aug 2021 23:22:12 +0300 > Maxim Devaev пишет: > > > Alan Stern wrote: > > > In other words, a device does not need to have an interrupt-OUT > > > endpoint, but if it does have one then the host must use it. > > > > You're right. Although the actual behavior of the hosts is not different > > from what I wrote - they really just ignore out endpoint. > > I will eventually fix this in the patch description. > > It seems that I have confused everything even more, sorry. I will explain. > There are three possible host behaviors: > > (1) The host works with the OUT endpoint as it describes the standard > and transmits reports through it. > > (2) The host works with IN endpoint, but refuses to transmit reports > via OUT endpoint at all. In the case of the keyboard, it will work, > but it will not receive the status of the LEDs. > > (3) The host sees OUT endpoint and either refuses to use such a device at all, > or goes crazy in various ways. > > In both cases (2) and (3), using SETUP/SET_REPORT solves the problem. > Therefore, I offer this as an option to solve compatibility problems. > Yes, in fact, this is not our problem, but it is impossible to fix the drivers > of all these proprietary devices. Moreover, I have never met a keyboard > with OUT endpoint, absolutely all of them use SETUP/SET_REPORT. Okay. I appreciate the more detailed explanations; thanks. Please resubmit the patch with appropriate changes to the description. Alan Stern