linux-kernel - Re: [PATCH v3 2/4] bus: fsl-mc: add restool userspace support

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Message-ID: <5AC63610.4000504@nxp.com>
Date:   Thu, 5 Apr 2018 14:43:29 +0000
From:   Laurentiu Tudor <laurentiu.tudor@....com>
To:     Andrew Lunn <andrew@...n.ch>
CC:     Stuart Yoder <stuyoder@...il.com>, Arnd Bergmann <arnd@...db.de>,
        Ioana Ciornei <ioana.ciornei@....com>,
        gregkh <gregkh@...uxfoundation.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Ruxandra Ioana Ciocoi Radulescu <ruxandra.radulescu@....com>,
        Razvan Stefanescu <razvan.stefanescu@....com>,
        Roy Pledge <roy.pledge@....com>,
        Networking <netdev@...r.kernel.org>
Subject: Re: [PATCH v3 2/4] bus: fsl-mc: add restool userspace support

Hi Andrew,

On 04/05/2018 03:48 PM, Andrew Lunn wrote:
>>> Hi Laurentiu
>>>
>>> So i can use switchdev without it? I can modprobe the switchdev
>>> driver, all the physical interfaces will appear, and i can use ip addr
>>> add etc. I do not need to use a user space tool at all in order to use
>>> the network functionality?
>>
>> Absolutely!
>
> Great.
>
> Then the easiest way forwards is to simply drop the IOCTL code for the
> moment. Get the basic support for the hardware into the kernel
> first. Then come back later to look at dynamic behaviour which needs
> some form of configuration.

Hmm, not sure I understand. We already have a fully functional ethernet 
driver [1] and a switch driver [2] ...

>> In normal use cases the system designer, depending on the requirements,
>> configures the various devices that it desires through a firmware
>> configuration (think something like a device tree). The devices
>> configured are presented on the mc-bus and probed normally by the
>> kernel. The standard networking linux tools can be used as expected.
>
> So what you should probably do is start a discussion on what this
> device tree binding looks like. But you need to be careful even
> here. Device tree describes the hardware, not how you configure the
> hardware. So maybe DT does not actually fit.

It's not an actual device tree, but a configuration file that happens to 
reuse the DTS format. I guess my analogy with a device tree was not the 
best.
Detailed documentation on the syntax can be found here [3], chapter 22.

[1] 
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/staging/fsl-dpaa2/ethernet
[2] 
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/staging/fsl-dpaa2/ethsw
[3] https://www.nxp.com/docs/en/user-guide/DPAA2_UM.pdf

---
Best Regards, Laurentiu