file upload class - problem with file_name config item

[eluser]Berik[/eluser]
Hi there,

Not sure if this is a bug or a misunderstanding on my part but when initialising the upload class with the file_name config item, the uploaded file is not renamed to what I feed it (it keeps the original file name).

Here's my upload function (within a controller):

Code:

function _upload()
    {
        $config['allowed_types'] = 'jpg|jpeg|gif|png';
        $config['upload_path'] = './uploads/';
        $config['file_name'] = 'name_of_file';
        $config['overwrite'] = FALSE;

        $this->load->library('upload', $config);
        if( ! $this->upload->do_upload('files'))
        {
            var_dump($this->upload->display_errors());
            exit;
        }

        // all ok, return file upload data
        $file_data = $this->upload->data();
        return $file_data;
    }

Any clue on what I could be doing wrong?