To fix the following error,

  CC      arch/powerpc/kernel/dma-mask.o
arch/powerpc/kernel/dma-mask.c:7:6: error: no previous prototype for 'arch_dma_set_mask' [-Werror=missing-prototypes]
    7 | void arch_dma_set_mask(struct device *dev, u64 dma_mask)
      |      ^~~~~~~~~~~~~~~~~

Move arch_dma_set_mask() definition into dma-map-ops.h and
include it in arch/powerpc/kernel/dma-mask.c

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Arnd Bergmann <arnd@arndb.de>
---
 arch/powerpc/kernel/dma-mask.c | 1 +
 include/linux/dma-map-ops.h    | 6 ++++++
 kernel/dma/mapping.c           | 6 ------
 3 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/arch/powerpc/kernel/dma-mask.c b/arch/powerpc/kernel/dma-mask.c
index ffbbbc432612..5b07ca7b73aa 100644
--- a/arch/powerpc/kernel/dma-mask.c
+++ b/arch/powerpc/kernel/dma-mask.c
@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0
 
 #include <linux/dma-mapping.h>
+#include <linux/dma-map-ops.h>
 #include <linux/export.h>
 #include <asm/machdep.h>
 
diff --git a/include/linux/dma-map-ops.h b/include/linux/dma-map-ops.h
index 9bf19b5bf755..6bca67e21bc1 100644
--- a/include/linux/dma-map-ops.h
+++ b/include/linux/dma-map-ops.h
@@ -509,4 +509,10 @@ pci_p2pdma_map_segment(struct pci_p2pdma_map_state *state, struct device *dev,
 }
 #endif /* CONFIG_PCI_P2PDMA */
 
+#ifdef CONFIG_ARCH_HAS_DMA_SET_MASK
+void arch_dma_set_mask(struct device *dev, u64 mask);
+#else
+#define arch_dma_set_mask(dev, mask)	do { } while (0)
+#endif
+
 #endif /* _LINUX_DMA_MAP_OPS_H */
diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c
index 9a4db5cce600..e323ca48f7f2 100644
--- a/kernel/dma/mapping.c
+++ b/kernel/dma/mapping.c
@@ -760,12 +760,6 @@ bool dma_pci_p2pdma_supported(struct device *dev)
 }
 EXPORT_SYMBOL_GPL(dma_pci_p2pdma_supported);
 
-#ifdef CONFIG_ARCH_HAS_DMA_SET_MASK
-void arch_dma_set_mask(struct device *dev, u64 mask);
-#else
-#define arch_dma_set_mask(dev, mask)	do { } while (0)
-#endif
-
 int dma_set_mask(struct device *dev, u64 mask)
 {
 	/*
-- 
2.41.0

On Fri, Aug 18, 2023, at 09:55, Christophe Leroy wrote:
> To fix the following error,
>
>   CC      arch/powerpc/kernel/dma-mask.o
> arch/powerpc/kernel/dma-mask.c:7:6: error: no previous prototype for 
> 'arch_dma_set_mask' [-Werror=missing-prototypes]
>     7 | void arch_dma_set_mask(struct device *dev, u64 dma_mask)
>       |      ^~~~~~~~~~~~~~~~~
>
> Move arch_dma_set_mask() definition into dma-map-ops.h and
> include it in arch/powerpc/kernel/dma-mask.c
>
> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
> Cc: Arnd Bergmann <arnd@arndb.de>
> ---

I sent the same patch, and this is already in linux-next as
3d6f126b15d9 ("dma-mapping: move arch_dma_set_mask() declaration
to header")

      Arnd