Nouveau - Jun 2019 - [PATCH 06/25] mm: factor out a devm_request_free_mem_region helper

On Mon, Jun 17, 2019 at 5:27 AM Christoph Hellwig <hch at lst.de>
wrote:
>
> Keep the physical address allocation that hmm_add_device does with the
> rest of the resource code, and allow future reuse of it without the hmm
> wrapper.
>
> Signed-off-by: Christoph Hellwig <hch at lst.de>
> Reviewed-by: Jason Gunthorpe <jgg at mellanox.com>
> Reviewed-by: John Hubbard <jhubbard at nvidia.com>
> ---
>  include/linux/ioport.h |  2 ++
>  kernel/resource.c      | 39 +++++++++++++++++++++++++++++++++++++++
>  mm/hmm.c               | 33 ++++-----------------------------
>  3 files changed, 45 insertions(+), 29 deletions(-)
>
> diff --git a/include/linux/ioport.h b/include/linux/ioport.h
> index da0ebaec25f0..76a33ae3bf6c 100644
> --- a/include/linux/ioport.h
> +++ b/include/linux/ioport.h
> @@ -286,6 +286,8 @@ static inline bool resource_overlaps(struct resource
*r1, struct resource *r2)
>         return (r1->start <= r2->end && r1->end >=
r2->start);
>  }
>
> +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'

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.

On Mon, Jun 17, 2019 at 07:40:18PM +0200, Christoph Hellwig
wrote:
> 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.
Actually, I could just move the patch to mark CONFIG_DEVICE_PUBLIC
broken earlier, which would force hmm_devmem_add to only be built
when CONFIG_DEVICE_PRIVATE ist set.