[Xenomai] Accessing an EtherCAT master from a Xenomai driver

[Xenomai] Accessing an EtherCAT master from a Xenomai driver

[Asier Tamayo]

Hello all,

I'm using IgH EtherCAT master for Linux, from EtherLab. I have a problem with accessing the master from a RTDM driver.

I've already asked this question in the EtherLab list, but have received no response, so I'm posting it here in case someone has worked with EtherLab but is no more in the mailing list.

My problem is the following:

I can access the EtherCAT master from a Xenomai user task, but have found no way to do it from a RTDM driver. In my tests, I have tried to follow the functions from the Xenomai example, but I find some problems I can't see how to resolve.

For instance, the Xenomai example (user space application) calls ecrt_master_activate(), which eventually calls rtdm_mmap_to_user(): in the RTDM driver, rtdm_mmap_to_user() is called with a user_info value set to NULL, and it crashes. Also, some functions have to be called in non-RT context. For example, ecrt_master_slave_config(), which allocates memory by causing a page fault.

I hope this time I'll have better luck. Best regards,


Asier Tamayo Arbide

Dpto I+D

R&D Department



ONA Electroerosión, s.a.



t      (34) 946 200 800

m    (34) 600 910 522

f      (34) 946 818 548

e      asier.tamayo@onaedm.com<mailto:asier.tamayo@onaedm.com>

w    www.onaedm.com<http://www.onaedm.com/>








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Re: [Xenomai] Accessing an EtherCAT master from a Xenomai driver

[Jan Kiszka]

On 2014-01-15 09:55, Asier Tamayo wrote:
> Hello all,
> 
> I'm using IgH EtherCAT master for Linux, from EtherLab. I have a problem with accessing the master from a RTDM driver.
> 
> I've already asked this question in the EtherLab list, but have received no response, so I'm posting it here in case someone has worked with EtherLab but is no more in the mailing list.
> 
> My problem is the following:
> 
> I can access the EtherCAT master from a Xenomai user task, but have found no way to do it from a RTDM driver. In my tests, I have tried to follow the functions from the Xenomai example, but I find some problems I can't see how to resolve.
> 
> For instance, the Xenomai example (user space application) calls ecrt_master_activate(), which eventually calls rtdm_mmap_to_user(): in the RTDM driver, rtdm_mmap_to_user() is called with a user_info value set to NULL, and it crashes. Also, some functions have to be called in non-RT context. For example, ecrt_master_slave_config(), which allocates memory by causing a page fault.
> 
> I hope this time I'll have better luck. Best regards,

The right address for your request remains the EtherLab Master project -
or you need to fix it yourself. Probably, their RTDM driver is not well
prepared for being used by other drivers and requires adaptions. Or
there are some details missing in the API documentation, e.g. that you
do not need to invoke that service which performs rtdm_mmap_to_user.
Moreover, from a quick look over it, EtherLab contains several
conceptual bugs /wrt RTDM API usage, so I would look carefully at the
whole thing.

Jan

-- 
Siemens AG, Corporate Technology, CT RTC ITP SES-DE
Corporate Competence Center Embedded Linux

Re: [Xenomai] Accessing an EtherCAT master from a Xenomai driver

[Asier Tamayo]

Dear Jan,

Thank you for your support. I think you're right when you say the Xenomai part of the EtherLab master is not finely tuned.

I may finally create a Xenomai task that accesses the EtherCAT RTDM driver, and let the other tasks communicate with the first one. However, I preferred the driver solution: better latency and better system structure (I could call the RTDM driver from another driver, both being at the same level).

If this solution doesn't work, I may try fixing the master myself.

> The right address for your request remains the EtherLab Master project -
>
I completely agree with you. As I wrote in my previous e-mail, I had already asked it there.

Best regards,

Asier Tamayo Arbide
Dpto I+D
R&D Department
 
ONA Electroerosión, s.a.
 
t      (34) 946 200 800
m    (34) 600 910 522
f      (34) 946 818 548
e      asier.tamayo@onaedm.com
w    www.onaedm.com
 
 
 
 
> -----Mensaje original-----
> De: Jan Kiszka [mailto:jan.kiszka@siemens.com]
> Enviado el: miércoles, 15 de enero de 2014 14:41
> Para: Asier Tamayo; xenomai@xenomai.org
> Asunto: Re: Accessing an EtherCAT master from a Xenomai driver
> 
> On 2014-01-15 09:55, Asier Tamayo wrote:
> > Hello all,
> >
> > I'm using IgH EtherCAT master for Linux, from EtherLab. I have a problem
> with accessing the master from a RTDM driver.
> >
> > I've already asked this question in the EtherLab list, but have received
> no response, so I'm posting it here in case someone has worked with
> EtherLab but is no more in the mailing list.
> >
> > My problem is the following:
> >
> > I can access the EtherCAT master from a Xenomai user task, but have
> found no way to do it from a RTDM driver. In my tests, I have tried to
> follow the functions from the Xenomai example, but I find some problems I
> can't see how to resolve.
> >
> > For instance, the Xenomai example (user space application) calls
> ecrt_master_activate(), which eventually calls rtdm_mmap_to_user(): in the
> RTDM driver, rtdm_mmap_to_user() is called with a user_info value set to
> NULL, and it crashes. Also, some functions have to be called in non-RT
> context. For example, ecrt_master_slave_config(), which allocates memory
> by causing a page fault.
> >
> > I hope this time I'll have better luck. Best regards,
> 
> The right address for your request remains the EtherLab Master project -
> or you need to fix it yourself. Probably, their RTDM driver is not well
> prepared for being used by other drivers and requires adaptions. Or
> there are some details missing in the API documentation, e.g. that you
> do not need to invoke that service which performs rtdm_mmap_to_user.
> Moreover, from a quick look over it, EtherLab contains several
> conceptual bugs /wrt RTDM API usage, so I would look carefully at the
> whole thing.
> 
> Jan
> 
> --
> Siemens AG, Corporate Technology, CT RTC ITP SES-DE
> Corporate Competence Center Embedded Linux