The Server Selection Spec says:

The current list of "may-use-secondary" commands includes:

• group
• mapreduce
• aggregate
• collStats, dbStats
• count, distinct
• geoNear, geoSearch, geoWalk
• parallelCollectionScan
• text

Associated command-specific helpers SHOULD take a read preference argument and otherwise MUST use the default read preference from client, database or collection configuration.

https://github.com/mongodb/specifications/blob/master/source/server-selection/server-selection.rst#use-of-read-preferences-with-commands

C Driver status:

• group - no helper function
• mapreduce - no helper function
• aggregate - up to spec, uses collection's read pref
• collStats, dbStats - we only have collStats, needs to be updated
• count, distinct - we only have count, needs to be updated
• geoNear, geoSearch, geoWalk - no helper functions
• parallelCollectionScan - no helper
• text - no helper