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

[Marek Szyprowski]

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@xxxxxxxxxx>
> Closes: https://lore.kernel.org/linux-next/acbjaDJ1a-YQC64d@xxxxxxxxxxxx/
> Signed-off-by: Maxime Ripard <mripard@xxxxxxxxxx>
> ---
> 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@xxxxxxxxxx
> ---
>  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.

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland