Re: Hardware Loopback on RT-Socket-CAN Needed

[Wolfgang Grandegger <wg@grandegger.com>]

Hello,

for RT-CAN related questions the Xenomai ML is maybe more appropriate.

Am 17.12.2015 um 15:43 schrieb Marc Kleine-Budde:
> On 12/17/2015 03:13 PM, Stephen Marshall wrote:
>> I am looking for some information on Loopback functionality for the
>> RT-Socket-CAN.
>
> You mean RT-Socket-CAN as in Xenomai? This is, as far as i know dead.

It's not dead! Just little contributions.

>> In Socket-CAN, we used to test the loopback functionality on own socket
>> using the flag *CAN_RAW_RECV_OWN_MSGS *using *MSG.CONFIRM* flag. However
>> in RT-Socket CAN we see that this option has been disabled purposefully.

Can't remember why it was not implemented. I think there was just no 
use-case,

[snip]

>> We use the SJA1000 CAN Controller and Xenomai 2.6. We tried setting the
>> SRR (Self Reception Request) bit at driver using *CAN_CTRLMODE_LOOPBACK*
>> <http://www.xenomai.org/documentation/xenomai-2.4/html/api/group__rtcan.html#ga19ec0cc4379e80c32cbd333cf7c145e9>*,

Are you still using Xenommai 2.4?

>> *however it was doing a software loopback where the looped back message
>> would not have actually gone in the bus. We needed the
>> CAN_RAW_RECV_OWN_MSGS fix at RT-Socket-CAN, could someone help?

IIRC, on the SJA1000 the hw loopback is redirecting tx messages to the 
rx unit (in hardware) without sending something out to the bus,

Have a look to:

 
https://git.xenomai.org/xenomai-2.6.git/tree/ksrc/drivers/can/rtcan_raw.c#n196

If you remove the "if" statement I think it already does what you want. 
But maybe I have missed something... it's a long time that I looked to 
that code.

Wolfgang.