You can not simply call do_upload method before initializing and setting config variables for the upload class.
You need to modify your code like this:
$config['upload_path'] = './assets/images/b2b/banner-agent/';
$config['allowed_types'] = 'gif|jpg|png';
$config['overwrite'] = TRUE;
$config['file_name'] = $banner2;
$this->load->library('upload'); //initialize
$this->upload->initialize($config); //Alternately you can set preferences by calling the initialize function. Useful if you auto-load the class
$this->upload->do_upload(); // do upload
if($this->upload->do_upload()){
$this->upload->data(); //returns an array containing all of the data related to the file you uploaded.
}
You can consult Codeigniter wiki for that too:
http://ellislab.com/codeigniter/user-guide/libraries/file_uploading.html
Hope this helps.
not working. We need some error message to work on.do_upload()?