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

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Message-ID: <CAGngYiUTHZFFY=H7xXHzZnN4pS0jAqWBTrcw04hjf5S-ykxC9w@mail.gmail.com>
Date:   Mon, 15 Apr 2019 14:31:45 -0400
From:   Sven Van Asbroeck <thesven73@...il.com>
To:     "Enrico Weigelt, metux IT consult" <lkml@...ux.net>
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

Hi Enrico,

Thanks for your input, appreciate it !

On Mon, Apr 15, 2019 at 1:41 PM Enrico Weigelt, metux IT consult
<lkml@...ux.net> wrote:
>
> AFAIK, "fieldbus" is a bit broader term than just the typical IEC61158-
> style remote memory stuff. At least that's the terminology my clients
> tend to use (eg. they also call some homebbrewn rs485-based protocols
> "fieldbus").
>
> Maybe it would be better calling it "IEC-61158" instead of "fieldbus" ?
>

Yes, we are certainly open to that, if it is more correct and/or better
accepted by users.

>
> By the way: can this device be opened/used by several processes
> simultaniously ?
>

Yes. You can open as many handles to the device as you like,
they will all share the fieldbus memory. When the remote
fieldbus memory changes, that event will be broadcast to
all open handles, via poll/select.

Of course if your application is monitoring the fieldbus memory
in more than one thread/process, you may need to guard
against race conditions. There is no guarantee which
thread/process will react to the change first.

Sven