Re: [PATCH 06/25] mm: factor out a devm_request_free_mem_region helper

[Christoph Hellwig]

On Mon, Jun 17, 2019 at 10:37:12AM -0700, Dan Williams wrote:
> > +struct resource *devm_request_free_mem_region(struct device *dev,
> > +               struct resource *base, unsigned long size);
> 
> This appears to need a 'static inline' helper stub in the
> CONFIG_DEVICE_PRIVATE=n case, otherwise this compile error triggers:
> 
> ld: mm/hmm.o: in function `hmm_devmem_add':
> /home/dwillia2/git/linux/mm/hmm.c:1427: undefined reference to
> `devm_request_free_mem_region'

*sigh* - hmm_devmem_add already only works for device private memory,
so it shouldn't be built if that option is not enabled, but in the
current code it is.  And a few patches later in the series we just
kill it off entirely, and the only real caller of this function
already depends on CONFIG_DEVICE_PRIVATE.  So I'm tempted to just
ignore the strict bisectability requirement here instead of making
things messy by either adding the proper ifdefs in hmm.c or providing
a stub we don't really need.