[PATCH 1/3] Adding page_offset_mask to device_dma_parameters

[Jianxiong Gao]

Some devices rely on the address offset in a page to function
correctly (NVMe driver as an example). These devices may use
a different page size than the Linux kernel. The address offset
has to be preserved upon mapping, and in order to do so, we
need to record the page_offset_mask first.

Signed-off-by: Jianxiong Gao <jxgao at google.com>
---
 include/linux/device.h      |  1 +
 include/linux/dma-mapping.h | 17 +++++++++++++++++
 2 files changed, 18 insertions(+)

diff --git a/include/linux/device.h b/include/linux/device.h
index 1779f90eeb4c..f44e0659fc66 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -292,6 +292,7 @@ struct device_dma_parameters {
 	 */
 	unsigned int max_segment_size;
 	unsigned long segment_boundary_mask;
+	unsigned int page_offset_mask;
 };
 
 /**
diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index 2e49996a8f39..5529a31fefba 100644
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -500,6 +500,23 @@ static inline int dma_set_seg_boundary(struct device *dev, unsigned long mask)
 	return -EIO;
 }
 
+static inline unsigned int dma_get_page_offset_mask(struct device *dev)
+{
+	if (dev->dma_parms)
+		return dev->dma_parms->page_offset_mask;
+	return 0;
+}
+
+static inline int dma_set_page_offset_mask(struct device *dev,
+		unsigned int page_offset_mask)
+{
+	if (dev->dma_parms) {
+		dev->dma_parms->page_offset_mask = page_offset_mask;
+		return 0;
+	}
+	return -EIO;
+}
+
 static inline int dma_get_cache_alignment(void)
 {
 #ifdef ARCH_DMA_MINALIGN
-- 
2.27.0