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=-4.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS 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 11F7CC433E1 for ; Fri, 24 Jul 2020 07:06:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D651B2073E for ; Fri, 24 Jul 2020 07:06:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1595574403; bh=+YLG2qLeBLkDNsiHP6bMhuRxbIR6vC8FzR2J5PtvCIM=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=e7++p9gOR5aX5iW7upeGWS7Xlosz2BYliakpP6ZLDXq81oVcUpk+OubURp+Vk2o3l /CK2bKkf5kKngAeejOdxwKpWbHVNzZsxXXel1W1d+MlN2ct2tAiFgfGTzja20wLn4m 5/zPjrEyb8zb7TSkuRDefcT6O5R5B0e9WzSV+vko= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726834AbgGXHGn (ORCPT ); Fri, 24 Jul 2020 03:06:43 -0400 Received: from mail.kernel.org ([198.145.29.99]:47072 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726817AbgGXHGn (ORCPT ); Fri, 24 Jul 2020 03:06:43 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 06FBD2073E; Fri, 24 Jul 2020 07:06:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1595574401; bh=+YLG2qLeBLkDNsiHP6bMhuRxbIR6vC8FzR2J5PtvCIM=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=11GlfwgFJOExQNvtnc+NnBxwoJa5wqaXIgfNXENAJcjRvqa1Dh9u8Zn9jmMODnHFy yxZF3xtAycwjsRccwKMSPOq/B4KeNw2ZhoXF+6e/7BILsgqDx467dWJ91FgxRZjRxB Xjg7EjXjcmAI7MWxsZES4t1eiwUE892vW4DnUQ+4= Date: Fri, 24 Jul 2020 09:06:43 +0200 From: Greg KH To: Mathias Nyman Cc: linux-usb@vger.kernel.org Subject: Re: [PATCH 00/27] xhci features for usb-next Message-ID: <20200724070643.GH3880088@kroah.com> References: <20200723144530.9992-1-mathias.nyman@linux.intel.com> <20200723150411.GA2529859@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-usb-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org On Thu, Jul 23, 2020 at 09:47:14PM +0300, Mathias Nyman wrote: > On 23.7.2020 18.04, Greg KH wrote: > > On Thu, Jul 23, 2020 at 05:45:03PM +0300, Mathias Nyman wrote: > >> Hi Greg > >> > >> This series for usb-next is almost completely about decoupling and > >> cleaning up relations between xhci, xhci debug capability (DbC), > >> and the DbC tty support. > >> > >> Real motivation behind this is to later turn DbC into a proper device > >> allowing us to bind different drivers to it, like dbctty. > > > > I don't really understand why you want to do that, but ok :) > > Well to be fair loading different drivers for DbC isn't the only motivation. > > Just using the Linux device model solves issues we are currently seeing > when using DbC on systems with several xHCI controllers. The original DbC > implementation didn't take this into account. I thought when that was first merged no one cared :) Nice to see that fixed here. > And as a bigger picture DbC is just one extended capability. > xHC controller provides a list of support extended capabilities, each one > with an ID and often a mmio region (inside xhci mmio range). > We don't handle these consistently in the xhci driver, for example > the role switch capability is currently turned into a platform device > while the DbC capability support is squashed all into the xhci driver. > > Long term idea here would be to create a extended capability bus where each > capability is a device, (child of xhci device) and drivers for these match > based on the capability ID. Odd, but ok. > > What is that going to help with? > > The option to load other drivers for the DbC capability will help other > developers to write "standard" Linux drivers that provide different interfaces > than TTY to send data over DbC. > > I don't fully understand these TTY limitations myself, but there is a strong push > to implement this, and the task to provide the infrastructure for this landed > on my table. What other interface is asked for? And yes, I would push back, what is wrong with TTY here? It should be the most "low overhead" interface that works with common userspace tools that we have. thanks, greg k-h