From: Philippe Gerum <rpm@xenomai.org>
To: Sunetra Sashi <snmgmt19@gmail.com>
Cc: xenomai@xenomai.org
Subject: Re: [Xenomai] XDDP and inter-driver API.
Date: Tue, 10 Jul 2012 19:09:10 +0200 [thread overview]
Message-ID: <4FFC61B6.4020900@xenomai.org> (raw)
In-Reply-To: <CAKSrRNz=88H6A_42fM0_vSSA2hpQekj_k25ZAmOH_Sja4m0TiQ@mail.gmail.com>
On 07/10/2012 06:15 PM, Sunetra Sashi wrote:
>
> Thanks for clarifying. I should have said ¨not possible using Xenomai
> IPCs¨. Sorry about that.
>
> I am not trying to port legacy code. I am instead trying to establish a
> communication pathway from voice applications in user land to some real
> time xenomai code running within the kernel via a linux driver KM
> running native linux. In our instance, it is necessary that the code
> executes in the kernel space.
I have a very simple question: would the real-time code implement a driver?
>
> On a related note, if I create a simple xenomai kernel module running
> real time code and signal events to it from linux kernel space (via the
> rt_event API) and communicate information back via interrupts (assuming
> we manage memory via shared buffers), would that considered to be a true
> Linux-Xenomai switch?
>
>
>
>
>
>
> On Tue, Jul 10, 2012 at 11:57 AM, Philippe Gerum <rpm@xenomai.org
> <mailto:rpm@xenomai.org>> wrote:
>
> On 07/10/2012 05:43 PM, Sunetra Sashi wrote:
>
>
>
> On Tue, Jul 10, 2012 at 11:01 AM, Philippe Gerum
> <rpm@xenomai.org <mailto:rpm@xenomai.org>
> <mailto:rpm@xenomai.org <mailto:rpm@xenomai.org>>> wrote:
>
> On 07/10/2012 01:23 PM, Sunetra Sashi wrote:
>
>
> What is the recommended methodology for kernel space
> modules to
> communicate with each other across the Linux-Xenomai space?
>
>
> There is no recommended methodology for this: kernel space
> should
> run within the linux domain only, or within the Xenomai
> domain only
> via the inter-driver RTDM interface, or should communicate with
> user-space only via a driver interface. rt <-> nrt within
> kernel
> space can be done using a low level mechanism, but there is
> no high
> level IPC for this.
>
> Again, if your kernel space code is actually an
> application, spare
> yourself a lot of pain, and move it to userland.
>
>
> That is interesting. So if I have a linux kernel module, say a
> network
> device driver. And another Xenomai kernel module that needs to
> run real
> time. Since we want to deal with IP packets, we need our linux
> module to
> run in the kernel space. Is it safe to assume that communication
> between
> 2 such drivers is not possible in the kernel?
>
>
>
> Where did you read the word "impossible" in any of my mails? I've
> been telling you two things:
>
> - the kind of interface you mention cannot be done using
> off-the-shelf Xenomai IPCs. It could be done with a low level
> interface though, hint: linux netdev interfacing to Xenomai APCs.
>
> - if your linux module actually runs an application, then you may
> want to consider moving it to userland, where it belongs. We
> strongly discourage implementing application code in kernel space.
>
> I don't know what you actually want to do, but it looks like some
> port of legacy code from say, VxWorks/pSOS/whatever to linux. If so,
> then you should reconsider your target software design, it looks
> wrong. There are better ways to do this, less error prone, more
> efficient and maintainable, provided you stop insisting on running
> application bits in kernel space.
>
>
>
> I corrected the rtipc rtdm device as a protocol device
> (I must have
> changed it in error) and I am able to load the
> xeno_rtipc.ko now.
> However, the socket open still fails with the same
> error code.
>
> Thanks
>
>
> I am making these calls from within the
> kernel, not
> from user space.
> Hence I ended up using rtdm calls instead
>
>
>
> /dev/rtp0 is a non-real-time user-space
> endpoint
> for the
> communication, between a regular linux
> application
> and a
> real-time
> component. It does not make sense to open
> it from
> kernel space.
>
>
> My intent here is to set up something similar to
> xddp-echo.c
> (RT - Non
> RT communication) but in kernel space instead. How
> should I go about
> creating the Linux endpoint for XDDP in the
> kernel?
>
>
> There is no direct way for that, this
> device/protocol is not
> intended for this purpose. This is a regular linux
> application to
> Xenomai real-time communication path, nothing
> else. Regular
> linux
> applications live in userland, only.
>
> We don't recommend building applications in kernel
> space.
>
>
>
>
>
>
>
> Do I need to install any
> specific xenomai
> modules for
> this to work?
>
>
> Obviously, yes. Check IPC
> drivers in the
> "Drivers"
> sub-menu
> of the
> Xenomai configuration. You need
> to have
> CONFIG_XENO_DRIVERS_RTIPC_XDDP
> enabled.
>
>
> I already checked this in the
> configuration,
> It is enabled.
> Should this
> also be set to y?
> CONFIG_XENO_DRIVERS_RTIPC. In my
> configuration
> it is
> set to m.
>
>
> Did you load the xeno_rtipc module then?
>
>
> It is not loaded. But I got an error when I
> did that.
> Xenomai: assertion failed at
> /.../kernel/xenomai/skins/)
> Xenomai: RTDM: missing open handler
>
>
> It does not make any sense. This assertion can
> only trigger
> for a
> named device, not a protocol device. RTIPC is a
> protocol
> device.
>
> - did you change any of the driver code?
> - what command did you use to load the module,
> verbatim?
>
> insmod: error inserting 'xeno_rtipc.ko': -1
> Invalid
> parameters
>
>
>
> Should I see any modules loaded in
>
> /proc/xenomai/rtdm/protocol_________devices?
>
>
> Yes.
>
>
>
>
> Thanks
> Shweta
>
>
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>
>
> --
> Philippe.
>
>
>
>
>
> --
> Philippe.
>
>
>
>
>
> --
> Philippe.
>
>
>
>
>
> --
> Philippe.
>
>
>
>
>
> --
> Philippe.
>
>
>
--
Philippe.
next prev parent reply other threads:[~2012-07-10 17:09 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-07-10 2:30 [Xenomai] XDDP and inter-driver API Sunetra Sashi
2012-07-10 8:40 ` Philippe Gerum
2012-07-10 9:03 ` Sunetra Sashi
2012-07-10 9:10 ` Philippe Gerum
2012-07-10 9:17 ` Sunetra Sashi
2012-07-10 9:36 ` Philippe Gerum
2012-07-10 11:23 ` Sunetra Sashi
2012-07-10 15:01 ` Philippe Gerum
2012-07-10 15:43 ` Sunetra Sashi
2012-07-10 15:57 ` Philippe Gerum
2012-07-10 16:15 ` Sunetra Sashi
2012-07-10 16:24 ` Lennart Sorensen
2012-07-10 17:00 ` Philippe Gerum
2012-07-10 17:09 ` Philippe Gerum [this message]
2012-07-10 17:20 ` Snmgmt
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