How to configuration McBSP3 and access it?

Hi All!
I am developing a driver on Android that can communicate with an external chip through McBSP3. I had search the example about it for long time. But none was found. So I grep the word “mcbsp” between the kernel files of android and find the files located in include/plat/mcbsp.h and arch/arm/plat-form/mcbsp.c. I include that header file, construct the data of type omap_mcbsp_reg_cfg, then call omap_mcbsp_config() with OMAP_MCBSP3 and the data of omap_mcbsp_reg_cfg as parameters. After that, the system dead. The error information tell me that a NULL pointer was referenced. I think it’s the pointer to McBSP3, because if I change the ID to OMAP_MCBSP1, no error occurred. My question is: how to construct the omap_mcbsp data for McBSP3? Should I reconfiguration the system?
Too little document can be find about this. I will be glad if someone would help me. Thank you!

Best Regards!
kenj