Attempt to build an out-of-tree RTC driver
Newcomer here, trying to properly use the RTC hardware of an STM32Lxx chip.
I wasn't able to build my driver attempt out-of-tree. It requires
`RTC` and `USE_STM32_LL_RTC` to be selected. Selecting the `RTC`
option results in the following build failure:
CMake Error at zephyr/CMakeLists.txt:503 (message):
The Zephyr library 'drivers__rtc' was created without source files. Empty
(non-imported) libraries are not supported. Either make sure that the
library has the sources it should have, or make sure it is not created when
it has no source files.
The second symbol is a hidden one, and there are some problems with
setting it's default from an application Kconfig file. Here is a
bare-bones app which tries to set it, and succeeds:
However, if BOARD is set in environment instead of cmake the
USE_STM32_LL_RTC symbol is not selected.
Given those, I'll work on my driver in-tree, but I hope you can shed
some light on the issues. I saw #5554 which was rejected because
subsystems should be in the driver. However, it seems out-of-tree
drivers for existing subsystems are still not easily doable still.