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 EB79FC433F5 for ; Mon, 31 Jan 2022 12:43:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241128AbiAaMni (ORCPT ); Mon, 31 Jan 2022 07:43:38 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40762 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234026AbiAaMng (ORCPT ); Mon, 31 Jan 2022 07:43:36 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DF28DC061714 for ; Mon, 31 Jan 2022 04:43:35 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id C0C5B61175 for ; Mon, 31 Jan 2022 12:43:34 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id AB115C340E8; Mon, 31 Jan 2022 12:43:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1643633014; bh=NjRVVJ5JSZ40aKWpgWapNcQntF6k3u0Rdqtz434OqXc=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=p+dWpSJubbF0QumjsU/H/ruNQqHKMCEcuWG1ScO7y7WQ9Sbu/GCcLwmmn/pj9Nkm0 YDQGVu+sfXnGUwr/fl6mGqV92Juxgl5tqhTK3U5VpZQtXPrdQM1BQUJNCWxWfWYQBe S8qp1KPYRnKBGAh4HFeu0+V/APElDhDAFDbtntdk= Date: Mon, 31 Jan 2022 13:43:31 +0100 From: Greg KH To: Kieran Bingham Cc: Alan Stern , Michael Grzeschik , linux-usb@vger.kernel.org, balbi@kernel.org, paul.elder@ideasonboard.com, laurent.pinchart@ideasonboard.com, kernel@pengutronix.de, nicolas@ndufresne.ca Subject: Re: [PATCH] dummy_hcd: add isoc support Message-ID: References: <164154749753.1224575.16682991529695492259@Monstersaurus> <20220126132249.2133168-1-m.grzeschik@pengutronix.de> <20220126183138.GB6506@pengutronix.de> <164363090018.533872.2376373763275566038@Monstersaurus> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <164363090018.533872.2376373763275566038@Monstersaurus> Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org On Mon, Jan 31, 2022 at 12:08:20PM +0000, Kieran Bingham wrote: > Hi Michael, Alan, > > Quoting Michael Grzeschik (2022-01-26 18:31:38) > > On Wed, Jan 26, 2022 at 11:09:23AM -0500, Alan Stern wrote: > > >On Wed, Jan 26, 2022 at 02:22:49PM +0100, Michael Grzeschik wrote: > > >> With this patch, the dummy_hcd gains first support for isoc transfers. > > >> It will complete the whole urb with all packages. > > > > > >"packets", not "packages". > > > > Right. > > > > >> Even if the gadget > > >> side did not enqueue any request, the urb will be handled. > > >> > > >> Signed-off-by: Michael Grzeschik > > > > > >I don't like this idea. If support for isochronous transfers is added, > > >it should be done correctly. That is, the implementation should support > > >scheduling of transfers, periodic bandwidth reservation, high-bandwidth > > >transfers, and so on. > > > > > >The whole point of dummy-hcd is to emulate a real host controller as > > >closely as possible. Real isochronous transfers do not complete all at > > >once. > > Being able to at least test uvc-gadget in a virtual environment would > already be a big benefit. As this is emulation, not simulation is it > essential that an exact mapping of the hardware is in place? Bindly being a sink for all data is not emulation for drivers that require some sort of feedback loop. > Is there anything we can do to support the progression of this > development? > > I.e. could we support this method first with a > WARN_ONCE("This does not fully emulate Isochronous support"); That would instantly trigger syzbot to send us reports for no good reason. Please don't do that :( thanks, greg k-h