Agreed, I ran into this exact thing in the last 48 hours or so working on a patch for the block module and looking at block hooks in general. A quick search shows that only block, forum and statistics core modules use 'configure' - so perhaps the rarity of its use kept it from being documented. But knowing that you can add configuration options to a block would certainly be helpful for module contributors. andre Moshe Weitzman wrote:
I am upgrading recipe.module now like a good citizen. I find these instructions unlikely:
"The only required changes to modules implementing hook_block() is to be careful about what is returned. Do not return anything if $op is not 'list' or 'view'".
But those are the only $op values according to http://drupaldocs.org/api/head/function/hook_block. Perhaps we need to document 'configure' and other operations? I have not followed these changes very closely.