If pMechanismList is not NULL_PTR, then *pulCount MUST contain the size (in terms of CK_MECHANISM_TYPE elements) of the buffer pointed to by pMechanismList.  If that buffer is large enough to hold the list of mechanisms, then the list is returned in it, and CKR_OK is returned.  If not, then the call to C_GetMechanismList returns the value CKR_BUFFER_TOO_SMALL.  In either case, the value *pulCount is set to hold the number of mechanisms.