rpmsg_client_sample linux kernel module loads automatically ?

[debugging]

STM32MP1Cube 1.1.0

Case:

1. unload /remove the module rpmsg_client_sample 
2. check lsmod the module is not loaded.
3. start the M4 with OpenAMP raw example

4. the rpmsg_client_sample  is automatically loaded.

Questions:

1. what is the mechanism behind how is this module loaded ?
2. How prevent this and manual load rpmsg_client_sample 
3. How to replace this module with a custom module to interact with the M4 code?

[Olivier GALLIEN]

Hi @debugging​ 

Find below answer from expert :

1. what is the mechanism behind how is this module loaded ?
2. How prevent this and manual load rpmsg_client_sample 

There are two mechanism involved

• automatic module loading is based on modeprobe. You can have a look at https://wiki.gentoo.org/wiki/Kernel_Modules for details.
  • RPMG bus mechanism that probes drivers registered if the name service defined matches. The principle is that on an end-point creation the cortex-M4 sends a “name service announcement�? message to the Linux. The RPMsg bus ( in Linux Kernel) checks for a Linux driver that supports this service name. If yes it probes the driver.  

1. How to replace this module with a custom module to interact with the M4 code?

I would suggest you to use the rpmsg_tty driver instead that creates a virtual UART communication between Linux application and the Cortex-M4

Olivier

[debugging]

@OliverG,

Many thanks. So I the driver rpmsg_client_sample must be removed when when building the kernel., correct?

Is there an easy way to find the drivers that match a certain “name service announcement" before starting a kernel build or at runtime ?

Thanks

[Olivier GALLIEN]

Hi @debugging​ 

registered drivers are listed in : /sys/bus/rpmsg/drivers

But to know associated services you need to dig into the code.

Olivier