netdev - Re: [PATCH v3 04/20] i40e: Register a virtbus device to provide RDMA

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Date:   Mon, 16 Dec 2019 09:17:28 +0000
From:   Parav Pandit <parav@...lanox.com>
To:     Greg KH <gregkh@...uxfoundation.org>
CC:     Jeff Kirsher <jeffrey.t.kirsher@...el.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        Shiraz Saleem <shiraz.saleem@...el.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>,
        "nhorman@...hat.com" <nhorman@...hat.com>,
        "sassmann@...hat.com" <sassmann@...hat.com>,
        "jgg@...pe.ca" <jgg@...pe.ca>,
        Mustafa Ismail <mustafa.ismail@...el.com>
Subject: Re: [PATCH v3 04/20] i40e: Register a virtbus device to provide RDMA

On 12/16/2019 2:28 PM, Greg KH wrote:
> On Mon, Dec 16, 2019 at 08:36:02AM +0000, Parav Pandit wrote:
>> On 12/16/2019 12:45 PM, Greg KH wrote:
>>> On Mon, Dec 16, 2019 at 03:48:05AM +0000, Parav Pandit wrote:
>> [..]
>>>>> I feel like the virtual bus code is getting better, but this use of the
>>>>> code, um, no, not ok.
>>>>>
>>>>> Either way, this series is NOT ready to be merged anywhere, please do
>>>>> not try to rush things.
>>>>>
>>>>> Also, what ever happened to my "YOU ALL MUST AGREE TO WORK TOGETHER"
>>>>> requirement between this group, and the other group trying to do the
>>>>> same thing?  I want to see signed-off-by from EVERYONE involved before
>>>>> we are going to consider this thing.
>>>>
>>>> I am working on RFC where PCI device is sliced to create sub-functions.
>>>> Each sub-function/slice is created dynamically by the user.
>>>> User gives sf-number at creation time which will be used for plumbing by
>>>> systemd/udev, devlink ports.
>>>
>>> That sounds exactly what is wanted here as well, right?
>>
>> Not exactly.
>> Here, in i40 use case - there is a PCI function.
>> This PCI function is used by two drivers:
>> (1) vendor_foo_netdev.ko creating Netdevice (class net)
>> (2) vendor_foo_rdma.ko creating RDMA device (class infiniband)
>>
>> And both drivers are notified using matching service virtbus, which
>> attempts to create to two virtbus_devices with different driver-id, one
>> for each class of device.
> 
> Yes, that is fine.
> 
>> However, devices of both class (net, infiniband) will have parent device
>> as PCI device.
> 
> That is fine.
> 
>> In case of sub-functions, created rdma and netdevice will have parent as
>> the sub-function 'struct device'. This way those SFs gets their
>> systemd/udev plumbing done rightly.
> 
> huh?  The rdma and netdevice will have as their parent device the
> virtdevice that is on the virtbus.  Not the PCI device's 'struct
> device'.
> 
Yes. I meant same when I said "sub-function 'struct device'", which is
nothing bug a virtdevice.

ok. Great. We are on same page now.

As we discussed, if sub-functions uses the bus, it will use the virtbus
and virtdevice device with above discussed differences.
Once I finish internal RFC review for sub-functions, will post it on the
list.
I do not expect RFC to finish before Christmas holidays.

Thanks,
Parav

> thanks,
> 
> greg k-h
>