linux-kernel - Re: [PATCH v10 6/7] usb: pci-quirks: add Intel USB drcfg mux device

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Date:	Fri, 17 Jun 2016 17:58:48 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	Lu Baolu <baolu.lu@...ux.intel.com>
Cc:	felipe.balbi@...ux.intel.com,
	Mathias Nyman <mathias.nyman@...el.com>,
	Lee Jones <lee.jones@...aro.org>,
	Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
	Liam Girdwood <lgirdwood@...il.com>,
	Mark Brown <broonie@...nel.org>, linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v10 6/7] usb: pci-quirks: add Intel USB drcfg mux device

On Thu, Jun 16, 2016 at 08:27:41AM +0800, Lu Baolu wrote:
> Hi Greg,
> 
> On 06/09/2016 10:39 AM, Lu Baolu wrote:
> > 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. :)
> 
> A gentle ping. :)

For what?  This patchset is long gone from my queue for the other
various things that came up with it, what can I do with it now?

> This port mux is not a PCI device. It only leverages the vendor
> specific capability defined in xhci specification for enumeration.

It's still crap :)

I don't know, and don't really remember the patch anymore anyway,
remember, I have the sort-term memory of a squirrel, you need repost
patches, with a proper changelog for me to be able to do anything...

greg k-h