From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1423673AbcFHPpa (ORCPT ); Wed, 8 Jun 2016 11:45:30 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:58000 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754316AbcFHPp3 (ORCPT ); Wed, 8 Jun 2016 11:45:29 -0400 Date: Wed, 8 Jun 2016 08:45:27 -0700 From: Greg Kroah-Hartman To: Lu Baolu 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 Subject: Re: [PATCH v10 6/7] usb: pci-quirks: add Intel USB drcfg mux device Message-ID: <20160608154527.GA16905@kroah.com> 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5757CF94.40803@linux.intel.com> User-Agent: Mutt/1.6.1 (2016-04-27) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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... greg k-h