Re: [PATCH v2 09/11] s390: mm: Convert to GENERIC_IOREMAP

[Christoph Hellwig]

> +void __iomem *
> +arch_ioremap(phys_addr_t *paddr, size_t size, unsigned long *prot_val)
>  {
>  	if (!static_branch_unlikely(&have_mio))
> +		return (void __iomem *) *paddr;
> +	return NULL;

This logic isn't new in the patch, but it could really use a comment
as it is rather non-obvious.