DCL Remote Control Patch for brickOS


The brickOS (formerly legOS) kernel should be extended, so that programs on the RCX can be started and stopped by a program running on a PC. This shouldn't require any changes on the user programs running on the RCX.


The default handler for LNP packages in the brickOS kernel has to be extended by two commands: "kill" stops all user programs (respectively all programs running on a lower priority than PRIO_HIGHEST!), start X starts the program no. X. Because the handler is implemented in the kernel, it is running during the whole power-on time of the RCX. A disadvantage is that the kernel has to be recompiled whenever the patch has to be changed.


The implementation can be found in rtm.c resp. rtm.h: rtm_handler(...) has to be registered on an arbitrary LNP port (by default it is just called in the default handler for port 0 - packet_producer(...) in program.c). The function copies according messages in a buffer, so that rtm_thread(...) can evaluate them (rtm_start(), called in kmain.c starts only this thread).

Unfortunately we had to change several locations in the kernel, because the number of running (kernel) threads was still hardcoded and checked against nb_tasks. All changes can be found by searching for CONF_RTM. But it seems that this has been changed in current brickOS versions!

Disvantages of this implementation: User threads aren't allowed to run in the highest priority and to change the default handler for port 0. Unfortunately this can't be checked easily.

The patch


Rename the (unpatched) brickOS/legOS directory to legOS:

mv legOS-0.2.x legOS

Patch the kernel:

patch -Np0 < rtm.patch

Further documentation

legOS Remote Task Management