Passing unique_ptr instead of * to method

I have a POD I use as a unique_ptr and lldb tells me its of type POD *. I have a free floating function I'd like to pass a reference of this POD to so I can populate public properties.

If I add a parameter of type POD * to the function, Clang has no problems compiling my code but if I try to pass unique_ptr<POD> &param or unique_ptr<POD param it fails with:

Candidate function not viable: no known conversion from ' *' to 'unique_ptr<>'

I thought I could always pass a unique_ptr where I'd have a raw pointer and vice-versa?

Update, method signature:

Original:

void connection_fsm(const LogLevel &level, const bytes &barray, unique_ptr<PGOutput> &output) noexcept;

vs

void connection_fsm(const LogLevel &level, const bytes &barray, unique_ptr<Conn> &conn, unique_ptr<PGOutput> &output) noexcept;

vs

void connection_fsm(const LogLevel &level, const bytes &barray, unique_ptr<Conn> conn, unique_ptr<PGOutput> &output) noexcept;

vs

void connection_fsm(const LogLevel &level, const bytes &barray, Conn *conn, unique_ptr<PGOutput> &output) noexcept;