[PATCH RFC 27/51] DMA-API: provide a helper to setup DMA masks

From: Russell King
Date: Thu Aug 01 2013 - 18:01:41 EST

Many drivers contain code such as:

dev->dma_mask = &dev->coherent_dma_mask;
dev->coherent_dma_mask = MASK;

Let's move this pattern out of drivers and have the DMA API provide a
helper for it. This helper uses dma_set_mask_and_coherent() to allow
platform issues to be properly dealt with via dma_set_mask()/

Signed-off-by: Russell King <rmk+kernel@xxxxxxxxxxxxxxxx>
include/linux/dma-mapping.h | 10 ++++++++++
1 files changed, 10 insertions(+), 0 deletions(-)

diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index 8f7a2e8..48ef6f5 100644
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -111,6 +111,16 @@ static inline int dma_set_mask_and_coherent(struct device *dev, u64 mask)
return rc;

+ * Similar to the above, except it deals with the case where the device
+ * does not have dev->dma_mask appropriately setup.
+ */
+static inline int dma_coerce_mask_and_coherent(struct device *dev, u64 mask)
+ dev->dma_mask = &dev->coherent_dma_mask;
+ return dma_set_mask_and_coherent(dev, mask);
extern u64 dma_get_required_mask(struct device *dev);

static inline unsigned int dma_get_max_seg_size(struct device *dev)

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