Is the extension interface not part of CV32E40X yet?

Created by: michael-platzer

Hi,

according to the README file of this project as well as the documentation the CV32E40X core "offers a general purpose extension interface" which allows to attach a coprocessor or similar extensions to the core "without the need to change the RTL of CV32E40X itself".

However, when scanning through the source code in the rtl/ directory I cannot find any sign of this extension interface. In fact, using grep it seems that none of the signals which should be part of the interface, such as x_issue_valid_o, or even typedefs such as x_issue_req_t are present in any file in this repository (except the documentation). It is mentioned in two issues though, #160 and #236 (closed), but apparently these only discuss the documentation of the interface.

Did I miss something or has this extension interface not been implemented yet?