# Re: \[PATCH v7 13/15\] dma-direct: Allocate memory from restricted DMA pool if available

- From: Christoph Hellwig \<hch@lst.de\>
- Date: 2021-05-27 13:30:57 
- List: linuxppc-dev
- Page: https://ratatoskr.run/linuxppc-dev/2021/05/1394051
- Thread: https://ratatoskr.run/linux-devicetree/2021/05/1381603/t.md

```text
> +#ifdef CONFIG_DMA_RESTRICTED_POOL
> +	if (swiotlb_free(dev, page, size))
> +		return;
> +#endif

Please avoid the ifdefs by either stubbing out the function to be a no-op
or by using IS_ENABLED.

> +#ifdef CONFIG_DMA_RESTRICTED_POOL
> +	page = swiotlb_alloc(dev, size);
> +	if (page && !dma_coherent_ok(dev, page_to_phys(page), size)) {
> +		__dma_direct_free_pages(dev, page, size);
> +		page = NULL;
> +	}
> +#endif

Same here, for the stub it would just return NULL.
```