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 DD33CC05027 for ; Thu, 2 Feb 2023 15:46:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232024AbjBBPqn (ORCPT ); Thu, 2 Feb 2023 10:46:43 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46258 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232771AbjBBPqk (ORCPT ); Thu, 2 Feb 2023 10:46:40 -0500 Received: from perceval.ideasonboard.com (perceval.ideasonboard.com [213.167.242.64]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EFD3B7B791 for ; Thu, 2 Feb 2023 07:46:11 -0800 (PST) Received: from [192.168.0.43] (cpc141996-chfd3-2-0-cust928.12-3.cable.virginm.net [86.13.91.161]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id D897D505; Thu, 2 Feb 2023 16:45:26 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1675352727; bh=ugJOnnTC1XRM6GChGM1XsXB3bm1on/4YomtpJkVQhhg=; h=Date:To:Cc:References:From:Subject:In-Reply-To:From; b=X5EhEOC0/55OkYNDt10WsDtAFr2zpDe4NOD0P5lb77rYH0mA3upptjyQ6pzlN/jQK MrXXyIFgRf2W+DW0fa8eCfxVpn0ImWlMB4TH1/vgxNYpR8TomTISceNRsyppqCX7A8 kJC0jtuQJYeFp+XOl9u/uMoq1ysFAo8LuyAgpn7s= Message-ID: <9da07e03-7cd2-cfeb-8c67-4562948aa948@ideasonboard.com> Date: Thu, 2 Feb 2023 15:45:24 +0000 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.4.2 Content-Language: en-US To: Alan Stern Cc: Thinh Nguyen , "linux-usb@vger.kernel.org" , rogerq@kernel.org References: <9ce226b4-90c6-94c4-a5ad-bd623409bc51@ideasonboard.com> <20230126002017.tbxc3j6xdgplncfs@synopsys.com> <20230126193131.ifaj7arsrrgesjh5@synopsys.com> <20230126235704.62d32y7y4sa4mmry@synopsys.com> <43b077ad-c8cd-bb49-134d-1bd66bed0b84@ideasonboard.com> From: Dan Scally Subject: Re: Explicit status phase for DWC3 In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org On 02/02/2023 14:52, Alan Stern wrote: > On Thu, Feb 02, 2023 at 10:12:45AM +0000, Dan Scally wrote: >> (+CC roger as the author of the USB_GADGET_DELAYED_STATUS mechanism) >> >> On 26/01/2023 23:57, Thinh Nguyen wrote: >>> We should already have this mechanism in place to do protocol STALL. >>> Please look into delayed_status and set halt. >> >> Thanks; I tried this by returning USB_GADGET_DELAYED_STATUS from the >> function's .setup() callback and later (after userspace checks the data >> packet) either calling usb_ep_queue() or usb_ep_set_halt() and it does seem >> to be working. This surprises me, as my understanding was that the purpose >> of USB_GADGET_DELAYED_STATUS  is to pause all control transfers including >> the data phase to give the function driver enough time to queue a request >> (and possibly only for specific requests). Regardless though I think the >> conclusion from previous discussions on this topic (see [1] for example) was >> that we don't want to rely on USB_GADGET_DELAYED_STATUS to do this which is >> why I had avoided it in the first place. A colleague made a series [2] some >> time ago that adds a flag to usb_request which function drivers can set when >> queuing the data phase request. UDC drivers then read that flag to decide >> whether to delay the status phase until after another usb_ep_queue(), and >> that's what I'm trying to implement here. >> >> >> [1] https://lkml.org/lkml/2018/10/10/138 >> >> [2] https://patchwork.kernel.org/project/linux-usb/patch/20190124030228.19840-5-paul.elder@ideasonboard.com/ > I'm in favor of the explicit_status approach from [2]. In fact, there > was a whole series of patches impementing this, and I don't think any of > them were merged. Yep, I'm picking that series up and want to get it merged. > Keep in mind that there are two separate issues here: > > Status/data stage for a control-IN or 0-length control-OUT > transfer. > > Status stage for a non-0-length control-OUT transfer. > > The USB_GADGET_DELAYED_STATUS mechanism was meant to help with the > first, not the second. explicit_status was meant to help with the > second; it may be able to help with both. Ack - thanks. That thread I linked was very informative, I wish I'd found it sooner! > Alan Stern