NUM_BDS_USED_FOR_NEXT_PTR
#define USABLE_BDS_PER_PAGE(bd_size,is_chain_mode) ((u32_t) (BD_PER_PAGE(bd_size)-NUM_BDS_USED_FOR_NEXT_PTR(bd_size,is_chain_mode)))
bd_chain->bds_skip_eop = NUM_BDS_USED_FOR_NEXT_PTR(bd_size,is_chain_mode);
bd_chain->bds_skip_eop = NUM_BDS_USED_FOR_NEXT_PTR(bd_size,is_chain_mode);