If you over allocate the number of analog channels this results in a
crash. It's easy to trigger this if you have voltage only monitors as we
still eat up a current input channel, regarless of if we use it. There
are only 16 channels at this time on ChibiOS, so if you have 9 voltage
only battery monitors you are out.
This PR improves that situation by only allocating channels when needed,
and in the case where we run out we now set a ConfigError, which on a
flight controller is much more friendly then a instant segfault the
moment we read a battery monitor. NOTE: on AP_Periph this takes the
node off the bus, rather then just sitting in the bootloader. This was
consideted acceptable as the current behaviour was to segfault and then
sit in the bootloader, unless you made new firmware that limited the
number of channels allocated it wasn't possible to recover in this
situation anyways.
Every backend stored a instance reference, which wasn't used in most locations
which is redundant given that the state already tracks the instance for us as
well.
This commit changes the way libraries headers are included in source files:
- If the header is in the same directory the source belongs to, so the
notation '#include ""' is used with the path relative to the directory
containing the source.
- If the header is outside the directory containing the source, then we use
the notation '#include <>' with the path relative to libraries folder.
Some of the advantages of such approach:
- Only one search path for libraries headers.
- OSs like Windows may have a better lookup time.
