[FAQ] RPMsg: How to add multiple endpoints to a remote core running RTOS?

The code changes

The attached patch adds two additional RPMsg endpoints that can be used to communicate with Linux userspace:

4760.0001-Linux_RPMsg_Echo-add-additional-endpoints.patch

Key details 

Each additional endpoint uses the same RPMsg service name that was defined for Linux userspace, "rpmsg_chrdev".

The expected service name for RPMsg endpoints that will communicate with Linux userspace is defined in the Linux rpmsg_char driver.

Each endpoint needs to have a separate RPMessage_Object with a unique semaphore in the RTOS-side code.

The way that TI has tested this is to give each endpoint a separate task in the RTOS-side code.

APPENDIX

How do I apply and build the code? 

For customers who are unfamiliar with applying git patch files, this is the process I use on the Linux terminal:

$ cd location/of/mcu+/sdk
$ git status
// we see no git repo has been created yet
$ git init
$ git add .
// create the initial commit by adding everything in the SDK
// this works best with a fresh SDK installation
$ git branch
// the master branch is the only branch
$ git branch featureBranchName
$ git checkout featureBranchName
// copy over the patch file
// now we can apply the patch
$ git apply patchFileName

Now I can build the project:

make -s -C examples/drivers/ipc/ipc_rpmsg_echo_linux/am64x-evm/r5fss0-0_freertos/ti-arm-clang all

For more information about building a specific project with a makefile from the terminal, reference the MCU+ SDK docs: https://software-dl.ti.com/mcu-plus-sdk/esd/AM64X/08_06_00_45/exports/docs/api_guide_am64x/MAKEFILE_BUILD_PAGE.html#MAKEFILE_EXAMPLE_BUILD

How do I load the firmware and test it?

For more information about loading a specific binary into a remote core from Linux, reference the Linux Academy: https://dev.ti.com/tirex/explore/node?a=7qm9DIS__LATEST&node=A__ANKEb6LZY6VAX.9xvGwQ-g__linux_academy_am64x__7qm9DIS__LATEST

For more information about testing IPC, reference the Linux Academy: https://dev.ti.com/tirex/explore/node?a=7qm9DIS__LATEST&node=A__AAtN.uvfmDSx4mvQ7f4R.w__linux_academy_am64x__7qm9DIS__LATEST

What should my output look like if I am testing the provided patch on AM64x? 

// code is running on R5F0_0, so use RPROC_ID 2

root@am64xx-evm:~# rpmsg_char_simple -r 2 -n 3 -d rpmsg_chrdev -p 14
Created endpt device rpmsg-char-2-986, fd = 3 port = 1024
Exchanging 3 messages with rpmsg device ti.ipc4.ping-pong on rproc id 2 ...

Sending message #0: hello there 0!
Receiving message #0: hello there 0!
Sending message #1: hello there 1!
Receiving message #1: hello there 1!
Sending message #2: hello there 2!
Receiving message #2: hello there 2!

Communicated 3 messages successfully on rpmsg-char-2-986

TEST STATUS: PASSED
root@am64xx-evm:~# rpmsg_char_simple -r 2 -n 3 -d rpmsg_chrdev -p 15
Created endpt device rpmsg-char-2-988, fd = 3 port = 1024
Exchanging 3 messages with rpmsg device ti.ipc4.ping-pong on rproc id 2 ...

Sending message #0: hello there 0!
Receiving message #0: hello there 0!
Sending message #1: hello there 1!
Receiving message #1: hello there 1!
Sending message #2: hello there 2!
Receiving message #2: hello there 2!

Communicated 3 messages successfully on rpmsg-char-2-988

TEST STATUS: PASSED
root@am64xx-evm:~# rpmsg_char_simple -r 2 -n 3 -d rpmsg_chrdev -p 16
Created endpt device rpmsg-char-2-990, fd = 3 port = 1024
Exchanging 3 messages with rpmsg device ti.ipc4.ping-pong on rproc id 2 ...

Sending message #0: hello there 0!
Receiving message #0: hello there 0!
Sending message #1: hello there 1!
Receiving message #1: hello there 1!
Sending message #2: hello there 2!
Receiving message #2: hello there 2!

Communicated 3 messages successfully on rpmsg-char-2-990

TEST STATUS: PASSED

// now let's see what happens if you talk to a nonexistent endpoint

root@am64xx-evm:~# rpmsg_char_simple -r 2 -n 3 -d rpmsg_chrdev -p 17
_rpmsg_char_find_ctrldev: could not find the matching rpmsg_ctrl device for virtio1.rp
msg_chrdev.-1.17
Can't create an endpoint device: Success
TEST STATUS: FAILED