ALso, in PX4 I can differentiate two errors on a read - the parameter does not exist, or it can't be read - but we don't know why. it might be corrupt perhaps, or perhaps they type is wrong.

Is it reasonable to add a specific MAV_PARAM_ERROR_READ_ERROR and a general MAV_PARAM_ERROR_TYPE_UNKNOWN_ERROR ?

ALso, in PX4 I can differentiate two errors on a read - the parameter does not exist, or it can't be read - but we don't know why. it might be corrupt perhaps, or perhaps they type is wrong.

Is it reasonable to add a specific MAV_PARAM_ERROR_READ_ERROR and a general MAV_PARAM_ERROR_TYPE_UNKNOWN_ERROR ?

Wouldn't that be MAV_PARAM_ERROR_TYPE_ERROR again?

If READ_ERROR is a thing on PX4 another entry seems warranted.

ALso, in PX4 I can differentiate two errors on a read - the parameter does not exist, or it can't be read - but we don't know why. it might be corrupt perhaps, or perhaps they type is wrong.
Is it reasonable to add a specific MAV_PARAM_ERROR_READ_ERROR and a general MAV_PARAM_ERROR_TYPE_UNKNOWN_ERROR ?

Wouldn't that be MAV_PARAM_ERROR_TYPE_ERROR again?

I guess it could be. Though why not MAV_PARAM_ERROR_TYPE_UNKNOWN?

If READ_ERROR is a thing on PX4 another entry seems warranted.

OK

I was also thinking perhaps

MAV_PARAM_ERROR_UNSUPPORTED_TYPE - to catch use of MAV_PARAM_TYPE_UINT8 say ?

OK, I think these are good now. @peterbarker Any issue before I squash merge?