He creado un sencillodatasource:

// app/Model/Datasource/FeedSource.php

App::uses('DataSource', 'Model/Datasource');

class FeedSource extends DataSource {
    public function abcd() {
        echo 'Hello World!';
    }
}

en midatabase.php:

public $feed = array(
    'datasource' => 'FeedSource'
);

Y enFeeda modelo:

class Feeda extends AppModel {
    public $useTable = false;
    public $useDbConfig = 'feed';
}

enlist controlador:

$this->loadModel('Feeda');
$this->Feeda->abcd();

Pero, devuelve un error fatal:

Error: Call to undefined method FeedSource::query()

¿Como resolverlo?

Gracias...