Man page 9 : dma_release_from_coherent

dma_release_from_coherent - try to free the memory allocated from per-device coherent memory pool

int dma_release_from_coherent(struct device *  dev , int  order , void *  vaddr );

dev
    device from which the memory was allocated

order
    the order of pages allocated

vaddr
    virtual address of allocated pages

This checks whether the memory was allocated from the per-device coherent memory pool and if so, releases that memory.

Returns 1 if we correctly released the memory, or 0 if dma_release_coherent should proceed with releasing memory from generic pools.