netdev - Re: [RFC 02/10] IB/hfi-vnic: Virtual Network Interface Controller (VNIC) Bus driver

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Date:   Mon, 21 Nov 2016 17:53:04 -0800
From:   "Vishwanathapura, Niranjana" <niranjana.vishwanathapura@...el.com>
To:     Jason Gunthorpe <jgunthorpe@...idianresearch.com>
Cc:     Doug Ledford <dledford@...hat.com>, linux-rdma@...r.kernel.org,
        netdev@...r.kernel.org,
        Dennis Dalessandro <dennis.dalessandro@...el.com>
Subject: Re: [RFC 02/10] IB/hfi-vnic: Virtual Network Interface Controller
 (VNIC) Bus driver

On Mon, Nov 21, 2016 at 04:31:18PM -0700, Jason Gunthorpe wrote:
>> >>>>+	ida_init(&hfi_vnic_ctrl_ida);
>> >>>>+	idr_init(&hfi_vnic_idr);
>> >>>>+
>> >>>>+	rc = bus_register(&hfi_vnic_bus);
>> >>>
>> >>>Why on earth do we need this? Didn't I give you enough grief for the
>> >>>psm stuff and now you want to create an entire subystem hidden away!?
>> >>>
>> >>>Use some netlink scheme to control your vnic like the rest of the net
>> >>>stack..
>> >>>
>> >>
>> >>The hfi_vnic_bus is only abstracting the HW independent functionality (like
>> >>Ethernet interface, encapsulation, IB MAD interface etc) with the HW
>> >>dependent functionality (sending/receiving packets on the wire).
>> >>Thus providing a cleaner interface between HW independent hfi_vnic Ethernet
>> >>and Control drivers and the HW dependent HFI1 driver.
>> >
>> >That doesn't explain anything, sound like you don't need it so get rid
>> >of it.
>
>> >>There is no other User interface here other than the standard Ethernet
>> >>interface through network stack.
>> >
>> >Good, then this isn't needed, because it doesn't provide a user interface.
>> >
>>
>> Can you explain what exactly you are asking to get rid of here and why?
>
>Get rid of the bus_register/etc as drivers do not get to call this.
>

There are many example drivers in kernel which are using bus_register() in
an initcall.
We could add a custom Interface between HFI1 driver and hfi_vnic drivers 
without involving a bus.
But using the existing bus model gave a lot of in-built flexibility in 
decoupling devices from the drivers.

Niranjana

>Jason