Re: [PATCH 2/7] mm: cma: Export cma_alloc and cma_release

[Maxime Ripard]

Hi David,

On Thu, Feb 26, 2026 at 11:25:24AM +0100, David Hildenbrand (Arm) wrote:
> On 2/25/26 17:41, Maxime Ripard wrote:
> > The CMA dma-buf heap uses cma_alloc() and cma_release() to allocate and
> > free, respectively, its CMA buffers.
> > 
> > However, these functions are not exported. Since we want to turn the CMA
> > heap into a module, let's export them both.
> > 
> > Signed-off-by: Maxime Ripard <mripard@xxxxxxxxxx>
> > ---
> >  mm/cma.c | 2 ++
> >  1 file changed, 2 insertions(+)
> > 
> > diff --git a/mm/cma.c b/mm/cma.c
> > index 94b5da468a7d719e5144d33b06bcc7619c0fbcc9..be142b473f3bd41b9c7d8ba4397f018f6993d962 100644
> > --- a/mm/cma.c
> > +++ b/mm/cma.c
> > @@ -949,10 +949,11 @@ struct page *cma_alloc(struct cma *cma, unsigned long count,
> >  	if (page)
> >  		set_pages_refcounted(page, count);
> >  
> >  	return page;
> >  }
> > +EXPORT_SYMBOL_GPL(cma_alloc);
> >  
> >  static struct cma_memrange *find_cma_memrange(struct cma *cma,
> >  		const struct page *pages, unsigned long count)
> >  {
> >  	struct cma_memrange *cmr = NULL;
> > @@ -1025,10 +1026,11 @@ bool cma_release(struct cma *cma, const struct page *pages,
> >  
> >  	__cma_release_frozen(cma, cmr, pages, count);
> >  
> >  	return true;
> >  }
> > +EXPORT_SYMBOL_GPL(cma_release);
> >  
> >  bool cma_release_frozen(struct cma *cma, const struct page *pages,
> >  		unsigned long count)
> >  {
> >  	struct cma_memrange *cmr;
> > 
> 
> I'm wondering whether we want to restrict all these exports to the
> dma-buf module only using EXPORT_SYMBOL_FOR_MODULES().

TIL about EXPORT_SYMBOL_FOR_MODULES, thanks.

> Especially dma_contiguous_default_area() (patch #4), I am not sure
> whether we want arbitrary modules to mess with that.

Yeah, I wasn't too fond about that one either. Alternatively, I guess we
could turn dev_get_cma_area into a non-inlined function and export that
instead?

Or we could do both.

Maxime

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