After commit 7844572c633964c864d9f32dc3f2a8ffe5d70371, dma_noop_ops are built only for architectures that use it.
For ARM architecture, CONFIG_DMA_NOOP_OPS is not selected, and cannot be selected. However, arch/arm/include/asm/dma-mapping.h is referencing dma_noop_ops: static inline const struct dma_map_ops *get_arch_dma_ops(struct bus_type *bus) { return IS_ENABLED(CONFIG_MMU) ? &arm_dma_ops : &dma_noop_ops; } I will let a maintainer suggest the best resolution for this :)