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

[Rob Herring]

On Thu, Oct 15, 2020 at 12:42 AM Christoph Hellwig <hch@xxxxxx> wrote:
>
> > +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.

I prefer that of_root is not more widely exposed and NULL regularly
means 'the whole tree'.

Rob