[PATCH v3 3/8] of/address: Introduce of_dma_get_max_cpu_address()

[Christoph Hellwig]

> +phys_addr_t __init of_dma_get_max_cpu_address(struct device_node *np)
> +{
> +	phys_addr_t max_cpu_addr = PHYS_ADDR_MAX;
> +	struct of_range_parser parser;
> +	phys_addr_t subtree_max_addr;
> +	struct device_node *child;
> +	phys_addr_t cpu_end = 0;
> +	struct of_range range;
> +	const __be32 *ranges;
> +	int len;
> +
> +	if (!np)
> +		np = of_root;

Requiring of_root to be passed explicitly would seem more natural
to me than the magic NULL argument.  There doesn't seem to be any
precedent for that kind of calling convention either.