FIXME: なにをするもの?
調査方法
$ grep -r EXPORT_SYMBOL drivers/staging/android/ion/ drivers/staging/android/ion/ion.c:EXPORT_SYMBOL(ion_alloc); drivers/staging/android/ion/ion.c:EXPORT_SYMBOL(ion_free); drivers/staging/android/ion/ion.c:EXPORT_SYMBOL(ion_phys); drivers/staging/android/ion/ion.c:EXPORT_SYMBOL(ion_map_kernel); drivers/staging/android/ion/ion.c:EXPORT_SYMBOL(ion_unmap_kernel); drivers/staging/android/ion/ion.c:EXPORT_SYMBOL(ion_client_create); drivers/staging/android/ion/ion.c:EXPORT_SYMBOL(ion_client_destroy); drivers/staging/android/ion/ion.c:EXPORT_SYMBOL(ion_sg_table); drivers/staging/android/ion/ion.c:EXPORT_SYMBOL(ion_share_dma_buf); drivers/staging/android/ion/ion.c:EXPORT_SYMBOL(ion_share_dma_buf_fd); drivers/staging/android/ion/ion.c:EXPORT_SYMBOL(ion_import_dma_buf); drivers/staging/android/ion/ion.c:EXPORT_SYMBOL(ion_device_add_heap); drivers/staging/android/ion/ion.c:EXPORT_SYMBOL(ion_device_create); drivers/staging/android/ion/ion.c:EXPORT_SYMBOL(ion_device_destroy); drivers/staging/android/ion/ion_heap.c:EXPORT_SYMBOL(ion_heap_create); drivers/staging/android/ion/ion_heap.c:EXPORT_SYMBOL(ion_heap_destroy);