netdev - Re: [PATCH v10 0/7] Add Fieldbus subsystem + support HMS Profinet card

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Message-ID: <23a25601-ed98-5348-9bac-bf8fc2baea5e@metux.net>
Date:   Tue, 16 Apr 2019 23:18:10 +0200
From:   "Enrico Weigelt, metux IT consult" <lkml@...ux.net>
To:     Sven Van Asbroeck <thesven73@...il.com>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Lee Jones <lee.jones@...aro.org>, mark.rutland@....com,
        Andreas Färber <afaerber@...e.de>,
        treding@...dia.com, David Lechner <david@...hnology.com>,
        noralf@...nnes.org, johan@...nel.org,
        Michal Simek <monstr@...str.eu>, michal.vokac@...ft.com,
        Arnd Bergmann <arnd@...db.de>,
        Greg KH <gregkh@...uxfoundation.org>, john.garry@...wei.com,
        geert+renesas@...der.be, robin.murphy@....com,
        Paul Gortmaker <paul.gortmaker@...driver.com>,
        sebastien.bourdelin@...oirfairelinux.com, icenowy@...c.io,
        Stuart Yoder <stuyoder@...il.com>,
        "J. Kiszka" <jan.kiszka@...mens.com>, maxime.ripard@...tlin.com,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH v10 0/7] Add Fieldbus subsystem + support HMS Profinet
 card

On 16.04.19 20:56, Sven Van Asbroeck wrote:

>> By the way: any special reason for doing this via device instead of
>> socket (like we have w/ can) ?
>>
> 
> A fieldbus_dev device communicates with its controller through a section
> of shared memory (process memory). It just felt more logical to model
> this as a device which acts like a file. When you read/write the file,
> you read/write the process memory underneath.

Yeah, that sounds logical. By the way: could we also mmap() that device?

Okay that's just a purely academical idea here, but I'm curious whether
that would make a notable difference in performance.

Yet another question: does each fieldbus_dev instance talk to exactly
one plc process memory, or can there be many ?

Having separate device nodes per plc process memory seems a good idea
for finer access control (via chown+friends).


--mtx

-- 
Enrico Weigelt, metux IT consult
Free software and Linux embedded engineering
info@...ux.net -- +49-151-27565287