netdev - Re: [RFC] ethtool: Support for driver private ioctl's

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Message-ID: <c9e4f4a4-bf58-6272-943e-5eeadeefdaa9@synopsys.com>
Date:   Fri, 6 Apr 2018 14:57:26 +0100
From:   Jose Abreu <Jose.Abreu@...opsys.com>
To:     Michal Kubecek <mkubecek@...e.cz>, <netdev@...r.kernel.org>
CC:     Florian Fainelli <f.fainelli@...il.com>,
        Jose Abreu <Jose.Abreu@...opsys.com>,
        David Miller <davem@...hat.com>,
        Jakub Jelinek <jj@...ra.linux.cz>,
        Jeff Garzik <jgarzik@...ox.com>, Tim Hockin <thockin@....com>,
        Eli Kupermann <eli.kupermann@...el.com>,
        Chris Leech <christopher.leech@...el.com>,
        Scott Feldman <scott.feldman@...el.com>,
        "Ben Hutchings" <ben@...adent.org.uk>,
        Joao Pinto <Joao.Pinto@...opsys.com>
Subject: Re: [RFC] ethtool: Support for driver private ioctl's

Hi Michal,

On 06-04-2018 10:07, Michal Kubecek wrote:
> On Thu, Apr 05, 2018 at 08:50:49AM -0700, Florian Fainelli wrote:
>> On 04/05/2018 03:47 AM, Jose Abreu wrote:
>>> Background: Synopsys Ethernet IP's have a certain number of
>>> features which can be reconfigured at runtime. Giving you two
>>> examples: One of the most recent one is the safety features,
>>> which can be enabled/disabled and forced at runtime. Another one
>>> is a Flexible RX Parser which can route specific packets to
>>> specific RX DMA channels. Given that these are features specific
>>> to our IP's it would not be useful to add an uniform API for this
>>> because the users would only be one or two drivers ...
>> Parsing of packets and directing the matched packets to specific
>> queues/channels can be done through ethtool rxnfc API, tc/cls_flower as
>> well, so you should really check whether those APIs don't already allow
>> you to do what you want.
>>
>> ethtool already supports a concept of private  flags, not ioctl() though
>> which allows you to toggle boolean values for instance (or technically
>> up to how many bits a "flag" is used to represent) is that enough or do
>> you need to turn on/off the feature as well as pass configuration
>> parameters?
> Perhaps introducing "driver/device specific tunables" (i.e. something
> like tunables or PHY tunables but specific to a particular device) could
> be a way. But it could get out of control quickly and users wouldn't be
> happy if they had to set the same (or almost the same) parameter under
> five different names for five NIC vendors.

Yeah, that wouldn't be good but I think this should be a
responsibility to developer: To see if there is an existing
API/ethtool entry before implementing the "tunable". I think a
big concern, for me at least, is that ethtool already has a lot
of options and introducing even more would lead the user to
confusion ...

Thanks and Best Regards,
Jose Miguel Abreu

>
> Michal Kubecek