nRF9160 select() always returns 115

RE: nRF9160 select() always returns 115

Albrecht Markus Schellenberger — Fri, 18 Jun 2021 06:40:23 GMT

Hello Gareth,

I just found out that nrf_select() is not supported yet within our implementation neither.

You might wanna have a look at the Zephyr implantation of the select() function and implement it to your OS?

However, that implementation is more of a "prosthesis" to make existing applications that require select() work and it is suggested to use poll() directly instead. But this might be something that you are already doing now?

Regards,

Markus

RE: nRF9160 select() always returns 115

Albrecht Markus Schellenberger — Wed, 16 Jun 2021 13:40:29 GMT

Hello again Gareth,

I’m unfortunately not quite sure if I can give you a proper answer to your question. Since the introduction of the nRF Connect SDK, our applications and libraries basically are based on the Zephyr RTOS. If we would have supported other operating systems, we would have announced that officially.

Of course that shouldn’t mean that it is not possible to use our libraries in other environments as well, but this is unfortunately nothing we have support for.

May I ask why you have decided to use your own OS instead of Zephyr?

Regards,

Markus

RE: nRF9160 select() always returns 115

Gareth — Fri, 11 Jun 2021 11:10:13 GMT

Hi Markus, thank you for following up with my select() enquiry. For clarification, I am receiving -1 in case of error, but I get 115 when I pull errno (i.e. that set by nrf_modem_os_errno_set()) . It is perhaps possible that select() is a function that does not set errno, though this seems unlikely as I had cleared errno prior to calling select().

Regardless, is there anywhere that it is publicly documented that select() only works under Zephyr? I'm just interested in understanding what I have missed, because I have sunk a lot of time into trying to understand something that was never going to work for me. If it's not documented, may I ask that it be added to the documentation of that function so others don't similarly get let astray?

Thanks again.

RE: nRF9160 select() always returns 115

Albrecht Markus Schellenberger — Fri, 11 Jun 2021 10:57:34 GMT

Hello again Gareth,

I now got some feedback from the modem team and it looks like that we do not have support or the nrf_select function outside of the Zephyr OS. As you can see in the documentation, the function returns -1 in case of error. Error number -115 is nothing that is supported by our implementation.

I hope this will answer your question.

Regards,

Markus

RE: nRF9160 select() always returns 115

Albrecht Markus Schellenberger — Mon, 07 Jun 2021 14:25:37 GMT

Thanks for the feedback, Gareth! It is really appreciated.

I’ll check the behaviour of the select() function with our modem team and come back to you.

Regards,

Markus

RE: nRF9160 select() always returns 115

Gareth — Fri, 04 Jun 2021 21:55:25 GMT

Hey Markus, thanks for your response. I have found that using poll() seems to work in my case (i.e. I wait on revent 0x2) and it seems to actually take ~100ms, which is what I would expect. That addresses my root issue.

I think I am unblocked for now in that respect, though I'm still concerned about the behaviour of select() and would quite like to understand what is going wrong there.

RE: nRF9160 select() always returns 115

Albrecht Markus Schellenberger — Fri, 04 Jun 2021 12:42:23 GMT

Hello Gareth,

I unfortunately do not have an answer to your questions right away. I have to check this internally and come back to you as soon as possible!

Regards,

Markus