Date:   Thu, 29 Dec 2016 17:28:24 +0530
From:   Kishon Vijay Abraham I <kishon@...com>
To:     Joao Pinto <Joao.Pinto@...opsys.com>,
        Bjorn Helgaas <helgaas@...nel.org>
CC:     Christoph Hellwig <hch@...radead.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        <linux-kernel@...r.kernel.org>, <linux-pci@...r.kernel.org>,
        <nsekhar@...com>, Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH] pci: rename *host* directory to *controller*

Hi,

On Thursday 29 December 2016 05:23 PM, Joao Pinto wrote:
> Às 11:48 AM de 12/29/2016, Kishon Vijay Abraham I escreveu:
>> Hi,
>>
>> On Thursday 29 December 2016 04:08 PM, Joao Pinto wrote:
>>>
>>> Hi,
>>>
>>> Às 5:46 AM de 12/29/2016, Kishon Vijay Abraham I escreveu:
>>>> Hi,
>>>>
>>>> On Wednesday 28 December 2016 10:50 PM, Joao Pinto wrote:
>>>>> Às 5:17 PM de 12/28/2016, Joao Pinto escreveu:
>>>>>> Às 4:41 PM de 12/28/2016, Bjorn Helgaas escreveu:
>>>>>>> On Wed, Dec 28, 2016 at 01:57:13PM +0000, Joao Pinto wrote:
>>>>>>>> Às 9:22 AM de 12/28/2016, Christoph Hellwig escreveu:
>>>>>>>>> On Wed, Dec 28, 2016 at 01:39:37PM +0530, Kishon Vijay Abraham I wrote:
>>>>>>>>>> As discussed during our LPC discussions, I'm posting the rename patch
>>>>>>>>>> here. I'll post the rest of EP series before the next merge window.
>>>>>>>>>>
>>>>>>>>>> There might be hiccups because of this renaming but feel this is
>>>>>>>>>> necessary for long-term maintenance.
>>>>>>>>>
>>>>>>>>> if we do this rename it would be great to get it to Linus NOW after
>>>>>>>>> -rc1 as that minimizes the impact on the 4.11 merge window.
>>>>>>>>
>>>>>>>> Rename it to controller is a bit vague I thing since we have the PCI Endpoint IP
>>>>>>>> also. Wouldn't be better to name it rc_controller?
>>>>>>>
>>>>>>> I think Kishon's whole goal is to add PCI Endpoint IP, so he wants a
>>>>>>> neutral name that can cover both RC and Endpoint.
>>>>
>>>> right.
>>>>>>>
>>>>>>> I'm not a huge fan of "controller" because it feels a little bit long
>>>>>>> and while I suppose it technically does include the concept of the PCI
>>>>>>> interface of an endpoint, it still suggests more of the host side to
>>>>>>> me.
>>>>>>>
>>>>>>> Doesn't USB have a similar situation?  I see there's a
>>>>>>> drivers/usb/host/ (probably where we copied from in the first place).
>>>>>>> Is a USB gadget the USB analog of what you're doing?  How do they
>>>>>>> share code between the master/slave sides?
>>>>>>>
>>>>>>
>>>>>> The usb/host contains the implemnentations by the spec of the several
>>>>>> *hci (USB Host) and then you can have for example the USB 3.0 Designware
>>>>>> Host specific ops in dwc3 and for USB 2.0 in dwc2/.
>>>>
>>>> right, each IP have a separate directory in USB. I thought of doing something
>>>> similar for PCI but decided against it since that would involve identifying all
>>>> the PCI IPs used and eventually result in more directories.
>>>>>> For device purposes it uses the core/ and then some of the device functions
>>>>>> are extended from the gadget/ package in which you can use mass_storage and
>>>>>> other types of functions.
>>>>
>>>> That would be similar for PCI endpoint. All endpoint specific core
>>>> functionality will be added in drivers/pci/endpoint (see RFC [1]).
>>>>>>
>>>>>> In our case in PCI we have the core functions inside /drivers/pci and the host
>>>>>> mangled inside host. I suggest:
>>>>>>
>>>>>> drivers/pci
>>>>>>  drivers/pci/core/
>>>>>>  drivers/pci/core/hotplug
>>>>>>  drivers/pci/core/pcie
>>>>>>  drivers/pci/core/<all other files inside pci/ today>
>>>>>>  drivers/pci/host
>>>>>>  drivers/pci/dwc -> here would be pcie-designware and the specific vendor drivers
>>>>>
>>>>> Correction:
>>>>> drivers/pci/host/dwc -> here would be pcie-designware and the specific vendor
>>>>> drivers
>>>>>
>>>>>>  drivers/pci/<vendorN> -> here would be the drivers for vendorN controller
>>>>>
>>>>> Correction:
>>>>> drivers/pci/host/<vendorN> -> here would be the drivers for vendorN controller
>>>>>
>>>>>>  drivers/pci/endpoint -> common code
>>>>>>  drivers/pci/endpoint/dwc -> implementation of Synopsys specific endpoint ops
>>>>>>  drivers/pci/<vendorN> -> implementation of other vendors specific endpoint ops
>>>>
>>>> There are some parts of the dwc driver that is common to both root complex and
>>>> endpoint. Where should that be? I'm sure no one wants to duplicate the common
>>>> piece in both root complex and endpoint.
>>>
>>> You are right, the config space is almost the same and some ops also common.
>>> I would suggest:
>>>
>>> drivers/pci
>>>   drivers/pci/core/
>>>     drivers/pci/core/hotplug
>>>     drivers/pci/core/pcie
>>>     drivers/pci/core/<all other files inside pci/ today>
>>>   drivers/pci/dwc
>>>     drivers/pci/dwc/common.c -> common ops and registers between RC and endpoint
>>>     drivers/pci/dwc/host/
>>>     drivers/pci/dwc/endpoint/
>>>
>>> What do you think?
>>
>> I don't think we should have sub-directories within dwc (USB too doesn't have
>> sub-directories). Where should the platform specific driver be kept? For
>> example pci-dra7xx.c (which use dwc) has both rc and ep specific parts but the
>> changes are so minimal that splitting the file won't make much sense.
>>
>> And such a change would also mean we create a separate directory for every
>> other driver present right now in pci/host.
> 
> I understand you idea. We can simplify it this way:
> 
>  drivers/pci
>    drivers/pci/core/
>      drivers/pci/core/hotplug
>      drivers/pci/core/pcie
>      drivers/pci/core/<all other files inside pci/ today>
>      drivers/pci/dwc -> Common files (RC and EP), specific vendor drivers for EP
> and EP
> 
> BTW dwc states for DesigWare Controller.
> 
> What do you think?

I'd like to avoid using different directory structures for different IPs. Lets
try to make it uniform.

Thanks
Kishon

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