How to get src and dst for pru_rpmsg_send?

How to get src and dst for pru_rpmsg_send?

[Andrew P. Lentvorski]

I seem to be missing something obvious: Where do I get the values for
src and dst in the pru_rpmsg_send() function?

The TI examples do a pru_rpmsg_receive() first and then echo back to the
same src and dst.  That seems ... odd.  What's the point of having a
variable src and dst if they are effectively hardwired to a single
communication channel?

Thanks.

Re: How to get src and dst for pru_rpmsg_send?

[Mathieu Poirier]

Hi Andrew,

On Wed, Feb 05, 2020 at 02:24:07AM -0800, Andrew P. Lentvorski wrote:
> I seem to be missing something obvious: Where do I get the values for
> src and dst in the pru_rpmsg_send() function?
> 
> The TI examples do a pru_rpmsg_receive() first and then echo back to the
> same src and dst.  That seems ... odd.  What's the point of having a
> variable src and dst if they are effectively hardwired to a single
> communication channel?

Since pru_rpmsg_send/receive() don't exist in the mainline kernel you will have
to be more specific... What TI examples are you referring to?  Where can we find
them? 

There are other rpmsg_sendxyz() functions that allow you to send messages to
different addresses[1].  Given the amount of information, I'm afraid there isn't
much else I can add at this time.

Thanks,
Mathieu  

[1]. https://elixir.bootlin.com/linux/latest/source/include/linux/rpmsg.h#L125


> 
> Thanks.

Re: How to get src and dst for pru_rpmsg_send?

[Andrew P. Lentvorski]

Hi, Mathieu,

On 2/5/20 3:21 PM, Mathieu Poirier wrote:
> Hi Andrew,
> 
> On Wed, Feb 05, 2020 at 02:24:07AM -0800, Andrew P. Lentvorski wrote:
>> I seem to be missing something obvious: Where do I get the values for
>> src and dst in the pru_rpmsg_send() function?
>>
>> The TI examples do a pru_rpmsg_receive() first and then echo back to the
>> same src and dst.  That seems ... odd.  What's the point of having a
>> variable src and dst if they are effectively hardwired to a single
>> communication channel?
> 
> Since pru_rpmsg_send/receive() don't exist in the mainline kernel you will have
> to be more specific... What TI examples are you referring to?  Where can we find
> them? 

TI keeps the examples here:
https://git.ti.com/cgit/pru-software-support-package/pru-software-support-package/

This is a good example of the rpmsg system being used with the echo I
talked about:
https://git.ti.com/cgit/pru-software-support-package/pru-software-support-package/tree/examples/am335x/PRU_RPMsg_Echo_Interrupt1

That example works on the Beaglebone Black (an am3359 based Linux board).

> There are other rpmsg_sendxyz() functions that allow you to send messages to
> different addresses[1].  Given the amount of information, I'm afraid there isn't
> much else I can add at this time.
> 
> Thanks,
> Mathieu  
> 
> [1]. https://elixir.bootlin.com/linux/latest/source/include/linux/rpmsg.h#L125

Thanks for the pointers.

It looks like I need to drag the src/dst out of the rpmsg_device or
rpmsg_channel_info on the Linux side and then pass it to the PRU side by
some method.  An initial message is as good as any and better than most.

I completely flaked that this wouldn't be in mainline.  Even a simple
thought about the name "*pru*_rpmsg_send" should have set off alarm
bells.  Sorry about that.

Thanks for the help,
-a