I use OpenLayers and GeoServer. I can read kml file format from OpenLayers. And I want to edit this polygon in kml. So I want polygon data(polygon circle and center coordinate etc..) to GeoServer.
For that, you could publish your polygon through a WFS-T Services and loading into your Open Layers viewer, allowing you to edit it.
Look at this example: http://openlayers.org/dev/examples/wfs-protocol-transactions.html
Keep in mind to set properly the proxy.cgi