This change prevents users from trying to use the `uorb_listener`
application without having floating point printing enabled on systems
that do not have an FPU (systems with FPUs have `LIBC_FLOATINGPOINT`)
enabled by default. Solution dicussed and agreed in:
https://github.com/apache/nuttx/issues/15599.
Listener can scan device under ORB_SENSOR_PATH, subscribe them and
cotinue printing messages by call their cb.
'-T' can Continuously print updating objects, '-l' means only
print once.
Signed-off-by: jihandong <jihandong@xiaomi.com>
Signed-off-by: Jiuzhu Dong <dongjiuzhu1@xiaomi.com>
refer to: https://docs.px4.io/v1.12/en/middleware/uorb.html
- orb_open: do real work for advertise() and subscribe(), if thre is
no user, register topic first, then save meta in driver;
only first user can successfully set buffer number.
- orb_exists: check topic state, if topic only has subscribers,
return "not exists".
Signed-off-by: jihandong <jihandong@xiaomi.com>
