I know that I can use the Show block for specific roles setting to manually configure whether a block is displayed to users.
I have a module that defines custom blocks. Rather than relying on the administrator to restrict the block visibility based on roles, can my module limit its blocks from being displayed unless a user has a particular permission?
Check access by user_access('Some access name');
For your module just return empty value, and block will not appear for that user.
For block admining, use php code for visibility.
Nikit is right, a code example would be:
<?php
$block = array();
if (user_access('my custom permission')) {
$block['content'] = t('Here is a message');
}
return $block;
?>
