rtnet code in rtai_24.1.12 (from denx)

deepa.vijayaraghavan at mbtech-group.com deepa.vijayaraghavan at mbtech-group.com
Mon Oct 25 14:25:02 CEST 2004


Hello Paolo,
   I tried using the file you had sent, to make socket calls from RTAI. As 
part of the init_module, I create socket(using ksocket()) and bind(using 
kbind) the server to the socket. This proceeds without errors.
  I spawn an idle task using rt_init_task(), also in the init_module(). 
When this task gets scheduled,  it checks the socket with the kpoll(), and 
sends the data out with the ksendto(). A call to kpoll() from the rt_task 
results in "StartedOops: kernel access of bad area, sig: 11" error. If I 
replace kpoll with poll, it goes through, but I get the oops for the 
ksendto call. I am unable to understand this! Any suggestion is of great 
help.

Thanks and Best Regards
Deepa.





  




mantegazza at aero.polimi.it
Gesendet von: rtai-admin at rtai.org
15.10.2004 18:40
 
        An:     deepa.vijayaraghavan at mbtech-group.com
        Kopie:  rtai at rtai.org
        Thema:  Re: rtnet code in rtai_24.1.12 (from denx)


deepa.vijayaraghavan at mbtech-group.com wrote:
> 
> 
> 
> Hello, Thanks a lot for the details.
> One newbie question:
> The code you have provided is an interface that enables calling the 
linux
> kernel socket interface directly from the RTAI module. Am I correct?
> How is RTNET different from this? I mean, since RTNET is hard real time, 
I
> think it does more in terms of converting the drivers etc., to enable 
hard
> realtime. Is my understanding correct?
> Hence, when I use the kernel socket calls, I do not have hard real time.
> For my application this interface is probably what I need. But as a 
person
> new to all this, I am just curious to learn & understand more.
> If you could point me to some documents/links that explain more about
> this(normal kernel drivers & hard realtime drivers), it will be great!
> 

Correct, the functions provided are not for real time, they use plain 
Linux.

I think there is no need for a more specific documentation. When in the 
need of using both Linux and RTNet for the same application you have to 
care of the coding. In RTAI netrpc.c there is the simple way we adopted. 
An example application integrating Linux and RTNet networking can be 
found at: http://www.aero.polimi.it/~mbdyn/mbdyn-rt/index.html.

Paolo.


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