Maximum 4 virtual uarts can be created?

[victor.b]

Hi,

As i was testing the limit of how many virtual uarts i can create, i found that the limit is actually 4:

Using debug tracing i can see that the channels get created inside the code (here i am creating 5 virtual uart) but only 4 ttyRPMSG are created.

I reduced the total buffer used by each channel to 256 instead of 512:

// File: rpmsg_virtio.h
 
/* Configurable parameters */
#ifndef RPMSG_BUFFER_SIZE
#define RPMSG_BUFFER_SIZE	(256)
#endif

So in theory, i should be able to create 8 channels but the max is 4 apparently.

Can someone please confirm how they made it?

Thanks

[OlivierK · Accepted solution]

Hi victor.b 

Thank you for your post, we discovered there was a bug in the rpmsg.c Cube FW library.

You should be able to create up to 32 instances of tty like it was originally tailored (( https://github.com/STMicroelectronics/linux/blob/v4.19-stm32mp/drivers/rpmsg/rpmsg_tty.c)

#define MAX_TTY_RPMSG_INDEX 32 /* Should be enough for a while */

Please find the fix here:

https://github.com/OpenAMP/open-amp/commit/efd67b0993d507ce3555f62fe46b414a8a8d4578

Best Regards,

Olivier