Re: [PATCH v2] dma/contiguous: Fix broken build

[Maxime Ripard <mripard@kernel.org>]

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Hi Marek,

On Mon, Mar 30, 2026 at 07:49:26PM +0200, Marek Szyprowski wrote:
> On 30.03.2026 17:40, Maxime Ripard wrote:
> > Commit 3a236f6a5cf2 ("dma: contiguous: Turn heap registration logic
> > around") didn't remove one last call to dma_heap_cma_register_heap()
> > that it removed, thus breaking the build.
> >
> > That last call is in dma_contiguous_reserve(), to handle the
> > registration of the default CMA region heap instance.
> >
> > The default CMA region instance is already somewhat handled by
> > retrieving it through the dev_get_cma_area() call in the CMA heap
> > driver. However, since commit 854acbe75ff4 ("dma-buf: heaps: Give
> > default CMA heap a fixed name"), we will create two heap instances for
> > the CMA default region.
> >
> > The first one is always called "default_cma_region", and is the one
> > handled by the call to dev_get_cma_area() mentioned earlier. The second
> > one is the name it used to have prior to that last commit for backward
> > compatibility.
> >
> > In the case where the default CMA region is defined in the DT, then that
> > region is registered through rmem_cma_setup() and that region is added
> > to the list of CMA regions to create a CMA heap instance for.
> >
> > In the case where the default CMA region is not defined in the DT
> > though used to be the case covered by the now removed
> > dma_heap_cma_register_heap() in dma_contiguous_reserve(). If we only
> > remove the call to dma_heap_cma_register_heap(), then the legacy name of
> > the CMA heap will not be registered anymore. We thus need to replace
> > that call with a call to rmem_cma_insert_area() to make sure we queue
> > this instance, if created, to create a heap instance.
> >
> > Once that call to dma_heap_cma_register_heap() replaced, we can also
> > remove the now unused function definition, its now empty header, and all
> > includes of this header.
> >
> > Fixes: 3a236f6a5cf2 ("dma: contiguous: Turn heap registration logic around")
> > Reported-by: Mark Brown <broonie@kernel.org>
> > Closes: https://lore.kernel.org/linux-next/acbjaDJ1a-YQC64d@sirena.co.uk/
> > Signed-off-by: Maxime Ripard <mripard@kernel.org>
> > ---
> > Changes in v2:
> > - Fix creation of the CMA heap instance with the legacy name when not
> >   declared in the DT. 
> > - Link to v1: https://lore.kernel.org/r/20260330-dma-build-fix-v1-1-748b64f0d8af@kernel.org
> > ---
> >  drivers/dma-buf/heaps/cma_heap.c  |  1 -
> >  include/linux/dma-buf/heaps/cma.h | 16 ----------------
> >  kernel/dma/contiguous.c           | 14 +++++++++++---
> >  3 files changed, 11 insertions(+), 20 deletions(-)
> >
> > diff --git a/drivers/dma-buf/heaps/cma_heap.c b/drivers/dma-buf/heaps/cma_heap.c
> > index 7216a14262b04bb6130ddf26b7d009f7d15b03fd..9a8b36bc929f6daa483a0139a2919d95127e0d23 100644
> > --- a/drivers/dma-buf/heaps/cma_heap.c
> > +++ b/drivers/dma-buf/heaps/cma_heap.c
> > @@ -12,11 +12,10 @@
> >  
> >  #define pr_fmt(fmt) "cma_heap: " fmt
> >  
> >  #include <linux/cma.h>
> >  #include <linux/dma-buf.h>
> > -#include <linux/dma-buf/heaps/cma.h>
> >  #include <linux/dma-heap.h>
> >  #include <linux/dma-map-ops.h>
> >  #include <linux/err.h>
> >  #include <linux/highmem.h>
> >  #include <linux/io.h>
> > diff --git a/include/linux/dma-buf/heaps/cma.h b/include/linux/dma-buf/heaps/cma.h
> > deleted file mode 100644
> > index e751479e21e703e24a5f799b4a7fc8bd0df3c1c4..0000000000000000000000000000000000000000
> > --- a/include/linux/dma-buf/heaps/cma.h
> > +++ /dev/null
> > @@ -1,16 +0,0 @@
> > -/* SPDX-License-Identifier: GPL-2.0 */
> > -#ifndef DMA_BUF_HEAP_CMA_H_
> > -#define DMA_BUF_HEAP_CMA_H_
> > -
> > -struct cma;
> > -
> > -#ifdef CONFIG_DMABUF_HEAPS_CMA
> > -int dma_heap_cma_register_heap(struct cma *cma);
> > -#else
> > -static inline int dma_heap_cma_register_heap(struct cma *cma)
> > -{
> > -	return 0;
> > -}
> > -#endif // CONFIG_DMABUF_HEAPS_CMA
> > -
> > -#endif // DMA_BUF_HEAP_CMA_H_
> > diff --git a/kernel/dma/contiguous.c b/kernel/dma/contiguous.c
> > index ad50512d71d3088a73e4b1ac02d6e6122374888e..d5d15983060c5c54744d6a63f2b591e1a3455b86 100644
> > --- a/kernel/dma/contiguous.c
> > +++ b/kernel/dma/contiguous.c
> > @@ -40,11 +40,10 @@
> >  #include <asm/page.h>
> >  
> >  #include <linux/memblock.h>
> >  #include <linux/err.h>
> >  #include <linux/sizes.h>
> > -#include <linux/dma-buf/heaps/cma.h>
> >  #include <linux/dma-map-ops.h>
> >  #include <linux/cma.h>
> >  #include <linux/nospec.h>
> >  
> >  #ifdef CONFIG_CMA_SIZE_MBYTES
> > @@ -217,10 +216,19 @@ static void __init dma_numa_cma_reserve(void)
> >  static inline void __init dma_numa_cma_reserve(void)
> >  {
> >  }
> >  #endif
> >  
> > +#ifdef CONFIG_OF_RESERVED_MEM
> > +static int rmem_cma_insert_area(struct cma *cma);
> > +#else
> > +static inline int rmem_cma_insert_area(struct cma *cma)
> > +{
> > +	return 0;
> > +}
> > +#endif
> > +
> >  /**
> >   * dma_contiguous_reserve() - reserve area(s) for contiguous memory handling
> >   * @limit: End address of the reserved memory (optional, 0 for any).
> >   *
> >   * This function reserves memory from early allocator. It should be
> > @@ -271,13 +279,13 @@ void __init dma_contiguous_reserve(phys_addr_t limit)
> >  						  &dma_contiguous_default_area,
> >  						  fixed);
> >  		if (ret)
> >  			return;
> >  
> > -		ret = dma_heap_cma_register_heap(dma_contiguous_default_area);
> > +		ret = rmem_cma_insert_area(dma_contiguous_default_area);
> >  		if (ret)
> > -			pr_warn("Couldn't register default CMA heap.");
> > +			pr_warn("Couldn't queue default CMA region for heap creation.");
> >  	}
> >  }
> >  
> >  void __weak
> >  dma_contiguous_early_fixup(phys_addr_t base, unsigned long size)
> >
> > ---
> 
> Huh, this is still not the correct fix to restore the old behavior.
> When !CONFIG_OF_RESERVED_MEM the default cma area should be still
> registered as the default cma dma-buf heap.

You're right, but it feels that it's a fundamental flaw in the original
patch rather than a quick fix for the build now. Can you drop the
patches you applied entirely? If so, I'll send a new version of that
series.

Maxime

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