Some cards are capable to announce if a specific profile is available or
not, effectively predicting whether a profile switch would fail or would
likely succeed. This can for example be useful for a UI that would gray
out any unavailable profile.
In addition, this information can be useful for internal modules
implementing automatic profile-switching policies, such as
module-switch-on-port-available or module-bluetooth-policy.
In particular, this information is essential when a port is associated
to multiple card profiles and therefore the port availability flag does
not provide enough information. The port "bluetooth-output" falls into
this category, for example, since it doesn't distinguish HSP/HFP from
A2DP.