[FAQ] AM625: How to get the Linux kernel RPMsg example working on Linux SDK 10.0, 10.1, 11.0?

What is the problem? 

RPMsg channels are created when a non-Linux core (or a "remote core") sends a name service announcement that contains the name of the service (i.e., the name of the channel). When a Linux driver is registered that has the same name, the remote core and the Linux driver can start sending each other RPMsg messages.

The upstream Linux version of the rpmsg_client_sample driver only uses the name "rpmsg-client-sample":
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/samples/rpmsg/rpmsg_client_sample.c

However, the MCU+ SDK example ipc_rpmsg_echo_linux registers the name "ti.ipc4.ping-pong" instead:
AM62x, AM62Ax, AM62Px: https://github.com/TexasInstruments/mcupsdk-core-k3/blob/k3_main/examples/drivers/ipc/ipc_rpmsg_echo_linux/ipc_rpmsg_echo.c
AM64x: https://github.com/TexasInstruments/mcupsdk-core/blob/next/examples/drivers/ipc/ipc_rpmsg_echo_linux/ipc_rpmsg_echo.c 

#define IPC_RPMESSAGE_SERVICE_PING        "ti.ipc4.ping-pong"
#define IPC_RPMESSAGE_ENDPT_PING          (13U)

Wait a minute... this example worked fine on Linux kernel 6.1 and earlier, right? 

On the ti-linux-kernel branch for Linux kernel 6.1 and earlier (i.e., Linux SDK 9.2 and earlier), we applied a patch that added "ti.ipc4.ping-pong" to the rpmsg_client_sample driver.
https://git.ti.com/cgit/ti-linux-kernel/ti-linux-kernel/commit/samples/rpmsg/rpmsg_client_sample.c?h=ti-linux-6.1.y&id=68874d652f2e82da56cb05ec1e998d2f5d600a69 

However, starting on Linux kernel 6.6 (Linux SDK 10.0 onwards), we no longer apply that patch. The channel names ti.ipc4.ping-pong and rpmsg-client-sample did not match, and the MCU+ SDK's ipc_rpmsg_echo_linux example stopped working with the sample kernel driver. (note that ipc_rpmsg_echo_linux still works with the Linux userspace example rpmsg_char_simple: https://git.ti.com/cgit/rpmsg/ti-rpmsg-char/ )

Workaround #1: patch the Linux driver 

One option to get the example working again is to simply apply the kernel patch that was manually applied to previous ti-linux-kernel branches:

https://git.ti.com/cgit/ti-linux-kernel/ti-linux-kernel/commit/samples/rpmsg/rpmsg_client_sample.c?h=ti-linux-6.1.y&id=68874d652f2e82da56cb05ec1e998d2f5d600a69 

This adds "ti.ipc4.ping-pong" to the rpmsg_client_sample driver.

Workaround #2: modify the MCU+ example code 

Another option is to modify the MCU+ ipc_rpmsg_echo_linux firmware to give it a service name of "rpmsg-client-sample".

AM62x, AM62Ax, AM62Px: https://github.com/TexasInstruments/mcupsdk-core-k3/blob/k3_main/examples/drivers/ipc/ipc_rpmsg_echo_linux/ipc_rpmsg_echo.c
AM64x: https://github.com/TexasInstruments/mcupsdk-core/blob/next/examples/drivers/ipc/ipc_rpmsg_echo_linux/ipc_rpmsg_echo.c 

Like this:

#define IPC_RPMESSAGE_SERVICE_PING        "rpmsg-client-sample"
#define IPC_RPMESSAGE_ENDPT_PING          (13U)