From: Sven Van Asbroeck <thesven73@gmail.com>
To: "Enrico Weigelt, metux IT consult" <lkml@metux.net>
Cc: "Rob Herring" <robh+dt@kernel.org>,
"Linus Walleij" <linus.walleij@linaro.org>,
"Lee Jones" <lee.jones@linaro.org>,
mark.rutland@arm.com, "Andreas Färber" <afaerber@suse.de>,
treding@nvidia.com, "David Lechner" <david@lechnology.com>,
noralf@tronnes.org, johan@kernel.org,
"Michal Simek" <monstr@monstr.eu>,
michal.vokac@ysoft.com, "Arnd Bergmann" <arnd@arndb.de>,
"Greg KH" <gregkh@linuxfoundation.org>,
john.garry@huawei.com, geert+renesas@glider.be,
robin.murphy@arm.com,
"Paul Gortmaker" <paul.gortmaker@windriver.com>,
sebastien.bourdelin@savoirfairelinux.com, icenowy@aosc.io,
"Stuart Yoder" <stuyoder@gmail.com>,
"J. Kiszka" <jan.kiszka@siemens.com>,
maxime.ripard@bootlin.com,
"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
netdev <netdev@vger.kernel.org>
Subject: Re: [PATCH v10 0/7] Add Fieldbus subsystem + support HMS Profinet card
Date: Tue, 16 Apr 2019 17:49:23 -0400 [thread overview]
Message-ID: <CAGngYiV4fj7TA1Apwc57oQMSjPW3mVKzfDoLbD2QJKw-GWNzBA@mail.gmail.com> (raw)
In-Reply-To: <23a25601-ed98-5348-9bac-bf8fc2baea5e@metux.net>
On Tue, Apr 16, 2019 at 5:21 PM Enrico Weigelt, metux IT consult
<lkml@metux.net> wrote:
>
> Yeah, that sounds logical. By the way: could we also mmap() that device?
AFAIK mmap only makes sense if you have actual device memory, accessible
through some memory controller. The process memory on anybus-s devices
is accessed through many layers of indirection, which includes a handshaking/
synchronization protocol over anybus-s.
In addition, you'd lose timing information about writes. The current API blocks
until the write to the remote PLC's process memory has been
successfully completed.
Perhaps if someone ever adds a fieldbus_dev driver for a device with mappable
process memory, we can consider mmap() as an optional extension ?
>
> Okay that's just a purely academical idea here, but I'm curious whether
> that would make a notable difference in performance.
Perhaps on a device with memory-mappable process memory.
But it would have to be an incredibly fast fieldbus device for the
difference between read()/write() and mmap() to matter...
>
> 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).
>
Good question ! I'll have to get back to you on that...
next prev parent reply other threads:[~2019-04-16 21:49 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-09 14:42 [PATCH v10 0/7] Add Fieldbus subsystem + support HMS Profinet card Sven Van Asbroeck
2019-04-09 14:42 ` [PATCH v10 1/7] fieldbus_dev: add Fieldbus Device subsystem Sven Van Asbroeck
2019-04-16 11:13 ` Greg KH
2019-04-09 14:42 ` [PATCH v10 2/7] anybus-s: support HMS Anybus-S bus Sven Van Asbroeck
2019-04-09 14:42 ` [PATCH v10 3/7] anybus-s: support the Arcx anybus controller Sven Van Asbroeck
2019-04-09 14:42 ` [PATCH v10 4/7] dt-bindings: anybus-controller: document devicetree binding Sven Van Asbroeck
2019-04-09 15:50 ` Rob Herring
2019-04-09 17:16 ` Sven Van Asbroeck
2019-04-09 17:31 ` Sven Van Asbroeck
2019-04-09 21:09 ` Rob Herring
2019-04-10 13:11 ` Sven Van Asbroeck
2019-04-16 11:11 ` Greg KH
2019-04-09 14:42 ` [PATCH v10 5/7] dt-bindings: Add vendor prefix for arcx / Archronix Sven Van Asbroeck
2019-04-09 14:42 ` [PATCH v10 6/7] fieldbus_dev: support HMS Profinet IRT industrial controller Sven Van Asbroeck
2019-04-09 14:42 ` [PATCH v10 7/7] staging: fieldbus_dev: add TODO Sven Van Asbroeck
2019-04-15 17:41 ` [PATCH v10 0/7] Add Fieldbus subsystem + support HMS Profinet card Enrico Weigelt, metux IT consult
2019-04-15 18:31 ` Sven Van Asbroeck
2019-04-16 16:49 ` Enrico Weigelt, metux IT consult
2019-04-16 18:56 ` Sven Van Asbroeck
2019-04-16 21:18 ` Enrico Weigelt, metux IT consult
2019-04-16 21:49 ` Sven Van Asbroeck [this message]
2019-04-16 22:12 ` Sven Van Asbroeck
2019-04-18 8:32 ` Enrico Weigelt, metux IT consult
2019-04-18 17:34 ` Sven Van Asbroeck
2019-04-24 9:40 ` Enrico Weigelt, metux IT consult
2019-04-24 10:26 ` Oliver Hartkopp
2019-04-24 11:00 ` Andreas Färber
2019-04-24 11:48 ` Oliver Hartkopp
2019-04-24 15:10 ` Sven Van Asbroeck
2019-04-29 13:54 ` Enrico Weigelt, metux IT consult
2019-04-17 14:37 ` Sven Van Asbroeck
2019-04-17 17:04 ` Andreas Färber
2019-04-17 20:13 ` Enrico Weigelt, metux IT consult
2019-04-25 8:26 ` Lee Jones
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