Function hipMemUnmap 

pub unsafe extern "C" fn hipMemUnmap(
    ptr: *mut c_void,
    size: usize,
) -> hipError_t

@brief Unmap memory allocation of a given address range.

@param [in] ptr - starting address of the range to unmap. @param [in] size - size of the virtual address range. @returns #hipSuccess, #hipErrorInvalidValue, #hipErrorNotSupported @warning This API is marked as Beta. While this feature is complete, it can change and might have outstanding issues.

@note This API is implemented on Linux and is under development on Microsoft Windows.