Enable debugging of DMA-API usage

modulename: debug.ko

and/or

dma-debug.ko

configname: CONFIG_DMA_API_DEBUG

Linux Kernel Configuration
└─>Enable debugging of DMA-API usage
In linux kernel since version 2.6.30 (release Date: 2009-06-09)  
Enable this option to debug the use of the DMA API by device drivers.
With this option you will be able to detect common bugs in device
drivers like double-freeing of DMA mappings or freeing mappings that
were never allocated.
This option causes a performance degredation. Use only if you want
to debug device drivers. If unsure, say N.

source code: