From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1426338AbcFICjf (ORCPT ); Wed, 8 Jun 2016 22:39:35 -0400 Received: from mga04.intel.com ([192.55.52.120]:25636 "EHLO mga04.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751949AbcFICjd (ORCPT ); Wed, 8 Jun 2016 22:39:33 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.26,442,1459839600"; d="scan'208";a="993988144" Subject: Re: [PATCH v10 6/7] usb: pci-quirks: add Intel USB drcfg mux device To: Greg Kroah-Hartman References: <1464831449-8973-1-git-send-email-baolu.lu@linux.intel.com> <1464831449-8973-7-git-send-email-baolu.lu@linux.intel.com> <20160608044518.GB3943@kroah.com> <5757CF94.40803@linux.intel.com> <20160608154527.GA16905@kroah.com> Cc: felipe.balbi@linux.intel.com, Mathias Nyman , Lee Jones , Heikki Krogerus , Liam Girdwood , Mark Brown , linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org From: Lu Baolu Message-ID: <5758D6E2.1000402@linux.intel.com> Date: Thu, 9 Jun 2016 10:39:30 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.5.1 MIME-Version: 1.0 In-Reply-To: <20160608154527.GA16905@kroah.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Greg, On 06/08/2016 11:45 PM, Greg Kroah-Hartman wrote: > On Wed, Jun 08, 2016 at 03:56:04PM +0800, Lu Baolu wrote: >> Hi Greg, >> >> On 06/08/2016 12:45 PM, Greg Kroah-Hartman wrote: >>> On Thu, Jun 02, 2016 at 09:37:28AM +0800, Lu Baolu wrote: >>>> In some Intel platforms, a single usb port is shared between USB host >>>> and device controllers. The shared port is under control of a switch >>>> which is defined in the Intel vendor defined extended capability for >>>> xHCI. >>>> >>>> This patch adds the support to detect and create the platform device >>>> for the port mux switch. >>> Why do you need a platform device for this? You do nothing with this >>> device, why create it at all? >> In this patch series, I have a generic framework for port mux devices >> and two port mux drivers sitting on top the generic code. >> >> In this patch, I create a platform device for the real mux device in >> Intel Cherry Trail or Broxton SOCs. In it's driver, I registered a mux >> into the generic framework and handle the power management >> things in driver's pm entries (otherwise, the system can't be waken >> up from system suspend).:) >> >>> And why is it a platform device, isn't is really a PCI device? Why >>> would you ever find a "platform" device below a PCI device? Don't abuse >>> platform devices for things that aren't. It makes me want to delete >>> that whole interface more and more... >> Port mux devices are physical devices in Intel Cherry Trail and Broxton >> SOCs. It doesn't sit on any PCIe bus. But it maps its registers in xHCI >> space. OS kernel can enumerate it by looking up the xhci extended >> capability list with a vendor specific capability ID. > A physical device that maps registers into PCI space seems like a PCI > device of some type to me :) > > Again, I hate platform devices for obvious reasons like this... > It's not PCI configure space, but xhci's io memory. XHCI spec reserves a range in its extended capability list for vendor specific things. Intel's platform leverages this for the port mux device register mapping. It looks odd though. :) Best regards, Lu Baolu