HP and Canon are supporting  each other on Patent infringement. Canon has been on a massive campaign against toner cartridge infringement. They have files suit against 49 sellers and distributors in the US. They have been going after third-party clone cartridges. They claim that intellectual property rights support research and development that drives innovation. The third party cartridges business for both Canon and HP equipment has become big business. 

The law suit is for toner cartridges but if successful inkjet cartridges are expected to follow.

HP in a statement by Andy Binder VP has stated that  " We support the efforts Canon is making to protect and defend iIntellectual property rights". Canon and HP are major competitors to each other in the toner and inkjet markets. They have also been suppliers to each other. Canon supplies HP with laser printer engines and some consumables