[v2,1/5] dma-mapping: Convert NO_DMA get_dma_ops() into a real dummy
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Message ID 1521206744-1504-2-git-send-email-geert@linux-m68k.org
State New, archived
Headers show
Series
  • Allow compile-testing NO_DMA (core)
Related show

Commit Message

Geert Uytterhoeven March 16, 2018, 1:25 p.m. UTC
If NO_DMA=y, get_dma_ops() returns a reference to the
non-existing symbol bad_dma_ops, thus causing a link failure if it is
ever used.

Make get_dma_ops() return NULL instead, to avoid the link failure.
This allows to improve compile-testing, and limits the need to keep on
sprinkling dependencies on HAS_DMA all over the place.

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Reviewed-by: Mark Brown <broonie@kernel.org>
Acked-by: Robin Murphy <robin.murphy@arm.com>
---
v2:
  - Add Reviewed-by, Acked-by,
  - Drop RFC state.
---
 include/linux/dma-mapping.h | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

Patch
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diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index eb9eab4ecd6d7a05..5ea7eec83c0fbb82 100644
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -212,14 +212,14 @@  static inline void set_dma_ops(struct device *dev,
 }
 #else
 /*
- * Define the dma api to allow compilation but not linking of
- * dma dependent code.  Code that depends on the dma-mapping
- * API needs to set 'depends on HAS_DMA' in its Kconfig
+ * Define the dma api to allow compilation of dma dependent code.
+ * Code that depends on the dma-mapping API needs to set 'depends on HAS_DMA'
+ * in its Kconfig, unless it already depends on <something> || COMPILE_TEST,
+ * where <something> guarantuees the availability of the dma-mapping API.
  */
-extern const struct dma_map_ops bad_dma_ops;
 static inline const struct dma_map_ops *get_dma_ops(struct device *dev)
 {
-	return &bad_dma_ops;
+	return NULL;
 }
 #endif