troubles with get_post_meta (and saving it)

here’s the complete code : if somebody could try it, i might doing something wrong, but i can’t find out what. (the whole code is inside a widget page)

/*
 *
 * add meta box : habillage
 *
 */
add_action( 'add_meta_boxes', 'myplugin_add_custom_box' );
add_action( 'save_post', 'myplugin_save_postdata' );

/* Adds a box to the main column on the Post and Page edit screens */
function myplugin_add_custom_box() {
add_meta_box(
    'test1',
    __( 'My test1', 'myplugin_textdomain' ),
    'myplugin_inner_custom_box',
    'post'
);
add_meta_box(
    'test2',
    __( 'My test2', 'myplugin_textdomain' ),
    'myplugin_inner_custom_box',
    'movies'
);
}


/* Prints the box content */
function myplugin_inner_custom_box() {
global $post;
// Use nonce for verification
wp_nonce_field( plugin_basename( __FILE__ ), 'myplugin_noncename' );
$met = get_post_meta($post->ID, 'champ', true)? get_post_meta($post->ID, 'champ', true) : 'empty meta';

    /* input */
echo '<label for="myplugin_new_field">';
_e("Description field : ", 'myplugin_textdomain' );
echo '</label> ';
echo '<input type="text" id="champ" name="champ" value="'.$met.'" />';




/* select list */
echo '<label for="my_list_field">';
_e("Description for this field", 'myplugin_textdomain' );
echo '</label> ';
echo '<select name="my_list_field" id="my_list_field">';

print_r ($post->ID);

global $post;

$s_query = new WP_Query( array(
'suppress_filters' => false,
'post_type' => 'movies'));
while($s_query->have_posts()):$s_query->the_post();

    $sname = $post->post_title;
    $s_output2 ='';
    $s_output2 .= '<option value="'.$post->ID.'" >';
    $s_output2 .= $post->post_title.' : allo';
    $s_output2 .= '</option>';
    echo $s_output2;

endwhile ;
echo '</select>';
wp_reset_query();
}


/* When the post is saved, saves our custom data */
function myplugin_save_postdata( $post_id ) {
  // verify if this is an auto save routine.
  // If it is our form has not been submitted, so we dont want to do anything
  if ( defined( 'DOING_AUTOSAVE' ) && DOING_AUTOSAVE )
      return;

  // verify this came from the our screen and with proper authorization,
  // because save_post can be triggered at other times
  if ( !wp_verify_nonce( $_POST['myplugin_noncename'], plugin_basename( __FILE__ ) ) )
  return;

  // Check permissions
  if ( 'page' == $_POST['post_type'] )
  {
    if ( !current_user_can( 'edit_page', $post_id ) )
    return;
  }
  else
  {
    if ( !current_user_can( 'edit_post', $post_id ) )
        return;
  }
  // OK, we're authenticated: we need to find and save the data
  //$mydata = $_POST['myplugin_new_field'];
  // Do something with $mydata
  // probably using add_post_meta(), update_post_meta()
  add_post_meta($post->ID, "champ_key", 'banana');

return $post_id;
//return $mydata;
}
?>