From: Rob Clark <rob@xxxxxx>
For devices which have constraints about maximum number of segments
in an sglist. For example, a device which could only deal with
contiguous buffers would set max_segment_count to 1.
The initial motivation is for devices sharing buffers via dma-buf,
to allow the buffer exporter to know the constraints of other
devices which have attached to the buffer. The dma_mask and fields
in 'struct device_dma_parameters' tell the exporter everything else
that is needed, except whether the importer has constraints about
maximum number of segments.
Signed-off-by: Rob Clark <rob@xxxxxx>
---
include/linux/device.h | 1 +
include/linux/dma-mapping.h | 16 ++++++++++++++++
2 files changed, 17 insertions(+)
diff --git a/include/linux/device.h b/include/linux/device.h
index 161d962..3813735 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -568,6 +568,7 @@ struct device_dma_parameters {
* sg limitations.
*/
unsigned int max_segment_size;
+ unsigned int max_segment_count; /* zero for unlimited */
unsigned long segment_boundary_mask;
};
diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index dfc099e..f380f79 100644
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -111,6 +111,22 @@ static inline unsigned int dma_set_max_seg_size(struct device *dev,
return -EIO;
}
+static inline unsigned int dma_get_max_seg_count(struct device *dev)
+{
+ return dev->dma_parms ? dev->dma_parms->max_segment_count : 0;
+}
+
+static inline int dma_set_max_seg_count(struct device *dev,
+ unsigned int count)
+{
+ if (dev->dma_parms) {
+ dev->dma_parms->max_segment_count = count;
+ return 0;
+ } else
+ return -EIO;
+}
+
+
static inline unsigned long dma_get_seg_boundary(struct device *dev)
{
return dev->dma_parms ?
--
1.7.9.5
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