Drupal Field API - Settings List - php

Question

I'm trying to create a 'link_field' in Drupal through a module, I've got the following code but I'd like to configure the field settings to do the following:
Not require title
Update the number of values to unlimited
I'm struggling to find any information around what setting key/pair values you can pass through for these, anyone able to offer some guidance on these?
<?php
/**
* Implements hook_enable().
*
* Create a field. Fields can be created without any needs to attach them to
* entities.
*/
function youtube_carousel_enable() {
$field = array(
'field_name' => 'ytcarousel_field',
'type' => 'link_field',
);
field_create_field($field);
/**
* Bind field to a entity bundle.
*/
$instance = array(
'field_name' => $field['field_name'],
'entity_type' => 'node',
'bundle' => 'homepage',
'label' => 'YouTube Video'
);
field_create_instance($instance);
}
/**
* Implements hook_disable().
*
* Remove field from node bundle (content type) and then delete the field.
*/
function youtube_carousel_disable() {
$instance = array(
'field_name' => 'ytcarousel_field',
'entity_type' => 'node',
'bundle' => 'homepage',
'label' => 'YouTube Video'
);
field_delete_instance($instance);
field_delete_field($instance['field_name']);
print 'Removed ' . $instance['field_name'] . "\n";
}
?>
Cheers

Answer 1

After viewing the HTML source to get key/value pairs I've managed to do something similar to the above with the following code:
<?php
/**
* Implements hook_enable().
*
* Create a field. Fields can be created without any needs to attach them to
* entities.
*/
function youtube_carousel_enable() {
$field = array(
'field_name' => 'ytcarousel_field',
'type' => 'link_field',
'cardinality' => -1
);
field_create_field($field);
/**
* Bind field to a entity bundle.
*/
$instance = array(
'field_name' => $field['field_name'],
'entity_type' => 'node',
'bundle' => 'homepage',
'label' => 'YouTube Video',
'settings' => array('title' => 'required')
);
field_create_instance($instance);
}
/**
* Implements hook_disable().
*
* Remove field from node bundle (content type) and then delete the field.
*/
function youtube_carousel_disable() {
$instance = array(
'field_name' => 'ytcarousel_field',
'entity_type' => 'node',
'bundle' => 'homepage',
'label' => 'YouTube Video',
'settings' => array('title' => 'required')
);
field_delete_instance($instance);
field_delete_field($instance['field_name']);
print 'Removed ' . $instance['field_name'] . "\n";
}
?>
The cardinality controls have many instances the value can have, "-1" is unlimited.
'cardinality' => -1
The title attribute is controlled via the instance not the field itself, I believe, and it uses text based values rather than numeric.
'settings' => array('title' => 'required')