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

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Date:	Sun, 19 Jun 2016 17:52:55 +0800
From:	Lu Baolu <baolu.lu@...ux.intel.com>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
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

Hi Greg,

On 06/18/2016 08:58 AM, Greg Kroah-Hartman wrote:
> 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?

I see now. Thanks for your reply.

Best regards,
Lu Baolu

>
>> 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
>