Load apps dynamically

[vChavezB]

Zephyr v3.5.0 allows dynamically loading elf files see Linkable Loadable Extensions (LLEXT)

Apps could be downloaded to the watch and loaded at run time.

Check the example at

https://github.com/zephyrproject-rtos/zephyr/tree/d2151aa114cbf389fdec972119b218f7b39f3c9b/tests/subsys/llext

For ZSwatch, it would be required to export the symbols that are used by the ZSwatch app API and the lvgl API

ZSWatch/app/src/managers/zsw_app_manager.h

Line 36 in 0f09e3c

int zsw_app_manager_show(on_app_manager_cb_fn close_cb, lv_obj_t *root, lv_group_t *group, char *app_name);

[Kampi]

Thanks for the suggestion @vChavezB

this requires an update of Zephyr (currently 3.4.99) but it looks like a good fit for the setup USB / Flash memory as the user can download the apps to the flash memory and they can be executed from the memory. But I like the idea behind it and it´s worth taking a look at it.

[jakkra]

Mm yeah I have looked at this, however my conclusions was that it's not mature enough. Apps need access to all of Zephyr, otherwise they will be quite limited. But maybe I miss something, I'm not too experienced in this area.

[vChavezB]

Zephyr includes some functions in the symbol table of llext through the EXPORT_SYMBOL macro.

From a search in Zephyr upstream these are the symbols available by default

Not that many, but if the apps requires more then these have to be added manually in the ZSwatch firmware through the MACRO (e.g. k_sleep, k_thread_create, etc ). And it makes sense, otherwise the symbol table would be too big, so its up to the user to export the symbols it needs based on the requirements of the project.

Another thing to consider is that currently the code as far as I understand does not support XIP. See zephyrproject-rtos/zephyr#63538

Just wanted to point out the technical details for implementation and what could be possible. I have worked with dynamically loading code on ARM before but it seems that its still a proof-of-concept. Nevertheless, a nice concept for future use in the watch.

[jakkra]

Right, each app can export whatever it needs, great idea!