netdev - Re: [for-next 4/6] net/mlx5: FPGA, Add basic support for Innova

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Date:   Fri, 26 May 2017 11:29:37 +0300
From:   Saeed Mahameed <saeedm@....mellanox.co.il>
To:     Jes Sorensen <jsorensen@...com>
Cc:     Ilan Tayari <ilant@...lanox.com>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Saeed Mahameed <saeedm@...lanox.com>,
        "David S. Miller" <davem@...emloft.net>,
        Doug Ledford <dledford@...hat.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>
Subject: Re: [for-next 4/6] net/mlx5: FPGA, Add basic support for Innova

On Thu, May 25, 2017 at 11:48 PM, Jes Sorensen <jsorensen@...com> wrote:
> On 05/25/2017 06:40 AM, Saeed Mahameed wrote:
>>
>> On Thu, May 25, 2017 at 8:20 AM, Ilan Tayari <ilant@...lanox.com> wrote:
>>>>
>>>> -----Original Message-----
>>>> Can you put it into different driver? Dumping everything into by far
>>>> the biggest nic driver already is already huge headache in terms on
>>>> maintainability, debugging and back ports.
>>>> Look at how intel splits their drivers.
>>>> ixgb, ixgbe, ixgbevf are different drivers thought they have a lot in
>>>> common. On one side it's a bit of copy paste, but on the other side
>>
>>
>> I don't think the ixgb example is the same, simply  ixgb, ixgbe,
>> ixgbevf have different PCI IDs
>> and even different SW/FW interfaces. On the other hand, same mlx5
>> driver can support all of
>> ConnetX4/5/6 device IDs with the same code flows, same interfaces.
>>
>>>> it makes drivers much easier to develop and maintain independently.
>>>> ConnectX-6 code and any future hw support doesn't belong to
>>>> mlx5 driver at all.
>>
>>
>> Sorry i must disagree with you on this for the same reasons Ilan
>> mentioned.
>> We can perfectly achieve the same with modular driver design all under the
>> same .ko module, with some kconfig flags to reduce the amount of
>> code/features
>> this .ko provides.
>
>
> If I get this right, the FPGA is independent and could in theory be used for
> non network stuff. It really should have it's own driver in that case, and
> you should provide accessor functionality via the mlx5 driver.
>

Hi Jes,

No, It is clearly stated in the commit message :

"The FPGA is a bump-on-the-wire and thus affects operation of
the mlx5_core driver on the ConnectX ASIC."

Which means mlx5 FPGA user can only write logic which affects only
packets going in/out
A ConnectX chip - so it is only network stuff -.

> We have this with other devices in the kernel where a primary device driver
> provides an interface for an additional sub-driver to access another device
> behind it. Like bt-coexist in some of the wifi drivers allowing access to a
> bluetooth device behind it.
>

Blutooth over wifi or vise versa is a very good example to what you
are requesting.
But, it doesn't fit to what we are trying to do here. mlx5 FGPA is a
ConnectX card feature, not a new protocol.

> Jes