Receiving "Operation Not Permitted" when setting RTCAN_RTIOC_RCV_TIMEOUT and reading from CAN over cobalt pthread

Josh Karch jkarch at
Wed Jul 1 16:55:35 CEST 2020


So a quick update, I was able to get the CAN drivers working, the issue as was suggested is that Linux did not register the interrupts for the Zynq, and I had to make a fake "generic-uio" module in the device tree to receive a valid IRQ number, and now the CAN core registers properly.

Now, I'm trying to create an application using the POSIX skin, based on the rtcanrecv.c example.  Rather than using rt_task_shadow, I'm using pthread_create.  My Makefile uses xeno-config with --skin=posix and sets --cflags and --ldflags, while wrap-link uses the POSIX ldflags. We are using libcobalt.

When I don't set the timeout IOCTL, my application runs, but it blocks indefinitely until messages are received, however when I set the IOCTL (0.1 sec)
ret = ioctl(can_fd, RTCAN_RTIOC_RCV_TIMEOUT, &timeout);
then make the read in my pthread

ret = recvfrom(can_fd, (void *)&can_msg_frame, sizeof(can_frame_t), 0,
                                  (struct sockaddr *)&can_address, &address_length);

I receive -EPERM rather than -ETIMEDOUT as a return.  The application is run as root, and works normally unless the TIMEOUT ioctl above is triggered;  thoughts on where to look?

Here are the lines of interest for the Makefile:
CFLAGS := $(shell $(DESTDIR)$(XENO_DIR)/$(XENO_CONFIG) --skin=posix --cflags)
LDFLAGS := $(shell $(DESTDIR)$(XENO_DIR)/$(XENO_CONFIG) --skin=posix --ldflags)

$(CC) -c  $(PROGNAME).c $(CFLAGS)

My guess is if I make the application run as an rt_task it would work.
Are there any special parameters needed to be set for pthread_create in order to run in RT mode?


Josh Karch

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