BlackBerry, on the block as its smartphone business struggles, is in talks with Cisco Systems, Google and SAP about selling them all or parts of itself, several sources close to the matter said. Such a deal would be an alternative to the preliminary agreement reached weeks ago with a group, led by BlackBerry’s biggest shareholder, Fairfax Financial Holdings, to take the company private for about $4.7 billion, a bid which has faced some skepticism because of financing questions. The company, based in Waterloo, Ontario, has asked for preliminary expressions of interest from potential strategic buyers, which also include Intel Corp and Asian companies LG and Samsung, by early next week. It is unclear which parties will bid, if any. But the potential technology buyers have been especially interested in BlackBerry’s secure server network and patent portfolio, although doubts about the assets’ value remain an issue, the sources said.