Le 07/02/2013 17:11, Gilles Chanteperdrix a écrit :
On 02/07/2013 03:53 PM, Stéphane LOS wrote:
Hello Sirs,
Hilscher is offering a Linux driver based on UIO for cifX boards.
In my understanding, down to 1ms cycle time, a PREEMPT RT solution
should be enough.
The cifX boards can manage with bus cycle times down to 250µs like with
EtherCAT or Sercos III firmwares.
So it seems in that cases that using Xenomai would be the way to go.
I suppose that it would be needed to modify or change the existing
driver but I can't figure out how things (Xenomai / RTDM / UIO) fit
together.
UIO is the kernel module that allows the mapping of the board memory to
user space.
The cifX driver uses the libpciaccess to pick up the board and retrieve
some board information from UIO before the mapping.
Then it uses pthread and rt functions when accessing the board.
Since UIO and libpciaccess are only used during the initialization, is
it a problem for a Xenomai application ?
We have setup a Xenomai system and tried to compile the user land
library with Xenomai options and flags and it seems we have been successful.
The driver should be using the POSIX skin of Xenomai if we have been lucky.
I can't see why we would need RTDM. Any hint please ?
I am an absolute beginner in the Xenomai arena, don't throw me to the
lions...
If UIO is used to register an interrupt handler for instance, the
interrupt handler will not be called in real-time context when used with
Xenomai, so, you would have to use the (deprecated) native or posix skin
services to register a user-space interrupt handler, or more likely
write an RTDM driver. On the other hand, if what you need is simply
accessing the board registers through MMIO, then you do not need RTDM.
While accessing registers from user-space may be tempting, there is a
risk of ending up with an application where the driver code is not
clearly separated. Writing a driver separated from the application is
preferable, as it provides a sane isolation between the two. If you
change the hardware, you just have to rewrite a driver which follows the
same profile, if you want to write another application using the same
driver, you can keep the driver.
Thank you for your kind support Gilles.
The cifX Device Driver is Hilscher's library to deal with cifX boards
and is available for the major OSes.
Additionally it is available to anybody as source code, the cifX Driver
Toolkit when one has to create a driver for his own OS.
This driver library accesses the board interface which is a Dual Port
Memory.
So the user application shall use this layer and gets independence from
the target OS.
I understand that we should create an RTDM driver instead of a UIO
driver and adapt the user library so that it uses the RTDM driver.
Am I right ?
I have seen also the Xenomai Solo project and the upcoming Xenomai 3
that would be using vanilla kernel with PREEMPT RT.
When this happens, would our RTDM based cifX driver still be an option
or would the UIO based driver suffice ?
Best Regards,
Cordialement,
Stéphane LOS
[email protected]
Support technique
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Hilscher France
12, rue du 35ème Régiment d'Aviation
Miniparc du Chêne
69500 BRON
France
Tél. : +33 (0) 4 72 37 98 40
Fax : +33 (0) 4 78 26 83 27
http ://www.hilscher.fr
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
_______________________________________________
Xenomai mailing list
[email protected]
http://www.xenomai.org/mailman/listinfo/xenomai
