From b866455423e040813f113d8b87e8297778ee2014 Mon Sep 17 00:00:00 2001
From: Christoph Hellwig <hch@lst.de>
Date: Tue, 16 Jul 2019 21:59:11 +0200
Subject: [PATCH] dma-mapping: add a dma_addressing_limited helper
This helper returns if the device has issues addressing all present
memory in the system.
Signed-off-by: Christoph Hellwig <hch@lst.de>
---
include/linux/dma-mapping.h | 14 ++++++++++++++
1 file changed, 14 insertions(+)
diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index 8d13e28a8e075..e11b115dd0e44 100644
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -679,6 +679,20 @@ static inline int dma_coerce_mask_and_coherent(struct device *dev, u64 mask)
return dma_set_mask_and_coherent(dev, mask);
}
+/**
+ * dma_addressing_limited - return if the device is addressing limited
+ * @dev: device to check
+ *
+ * Return %true if the devices DMA mask is too small to address all memory in
+ * the system, else %false. Lack of addressing bits is the prime reason for
+ * bounce buffering, but might not be the only one.
+ */
+static inline bool dma_addressing_limited(struct device *dev)
+{
+ return min_not_zero(*dev->dma_mask, dev->bus_dma_mask) <
+ dma_get_required_mask(dev);
+}
+
#ifdef CONFIG_ARCH_HAS_SETUP_DMA_OPS
void arch_setup_dma_ops(struct device *dev, u64 dma_base, u64 size,
const struct iommu_ops *iommu, bool coherent);
--
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