Validation problem for form_upload

[eluser]Sawariya[/eluser]
function do_upload()
{
$config['upload_path'] = './uploads/';
$config['allowed_types'] = 'gif|jpg|png';
$config['max_size'] = '100';
$config['max_width'] = '1024';
$config['max_height'] = '768';

$this->load->library('upload', $config);

if ( ! $this->upload->do_upload())
{
$arr= array('error' => $this->upload->display_errors());

$this->load->view('upload_form', $arr);
}
else
{
$data = array('upload_data' => $this->upload->data());

$this->load->view('upload_success', $data);
}
}