tree 2020d75b1ad0e75a359f42ccba5466a1fccb9f91
parent 1d78a47c28f44e8e8b30d85311770d0a4e6a1364
author Matt Spinler <spinler@us.ibm.com> 1605017703 -0600
committer Matt Spinler <spinler@us.ibm.com> 1605198500 -0600

Tolerate missing sensors on startup

Instead of crashing if one of the sensors listed in the symbol table
isn't on D-Bus yet, return quiet_NaN for its value instead.  A quiet_NaN
is what most of the sensor applications (all of the dbus-sensors ones)
return anyway when they are not able to read the device, and this can be
considered similar to that - that the device isn't accessible yet.

This eases the dependencies necessary in the service file, as the
service file as it stands now doesn't wait for any sensor providing
services to start, and even if it did different virtual sensors could
require different dependencies.

An alternative would be to have the code not even put the virtual sensor
on D-Bus until all of its required sensors are available, but that adds
quite a bit of complexity when usually there will just be a small window
after a reboot when the services area all starting up that this would
occur.

Signed-off-by: Matt Spinler <spinler@us.ibm.com>
Change-Id: Ifc9b010774fa1a703ff660abe57c57220cc907b3